diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index bea7cac..f8c2c08 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -14,7 +14,7 @@ jobs:
       image: shiguredo/erlang:otp-27.0.1-openssl-3.3.1-ubuntu-24.04-x86_64
     steps:
       - uses: actions/checkout@v4
-      - run: make
+      - run: make ci
       - name: Slack Notification
         if: failure()
         uses: rtCamp/action-slack-notify@v2
diff --git a/CHANGES.md b/CHANGES.md
index 0606bcb..6741d51 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -4,6 +4,9 @@
 
 - [CHANGE] rebar3 の minimum_otp_vsn を 27.0 にする
   - @voluntas
+- [ADD] PBT を追加
+  - clockwork のみ
+  - @voluntas
 - [UPDATE] rebar3 3.23.0 に更新する
   - @voluntas
 - [UPDATE] GitHub Actions の docker の OTP を 27.0.1 / OpenSSL 3.3.1 に上げる
diff --git a/Makefile b/Makefile
index 93bf583..653dc4a 100644
--- a/Makefile
+++ b/Makefile
@@ -1,6 +1,6 @@
-.PHONY: all upgrade compile test dialyzer clean github
+.PHONY: all upgrade compile dialyzer test proper clean ci publish
 
-all: clean upgrade compile test dialyzer
+all: clean upgrade compile dialyzer test proper
 
 upgrade:
 	@./rebar3 do update, upgrade --all
@@ -8,19 +8,19 @@ upgrade:
 compile:
 	@./rebar3 xref
 
+dialyzer:
+	@./rebar3 dialyzer
+
 test:
 	@./rebar3 as test eunit, cover
 
-dialyzer:
-	@./rebar3 dialyzer
+proper:
+	@./rebar3 as test proper
 
 clean:
 	@./rebar3 clean
 
-github:
-	$(MAKE) compile
-	$(MAKE) dialyzer
-	$(MAKE) test
+ci: compile dialyzer test proper
 
 publish:
 	@./rebar3 hex publish package
diff --git a/rebar.config b/rebar.config
index 745f289..0b9f8e1 100644
--- a/rebar.config
+++ b/rebar.config
@@ -35,3 +35,8 @@
 {elvis_output_format, colors}.
 
 {plugins, [rebar3_hex]}.
+
+{profiles,
+ [{test,
+   [{plugins, [rebar3_proper]},
+    {deps, [{proper, {git, "https://github.com/proper-testing/proper", {branch, "master"}}}]}]}]}.
diff --git a/test/prop_base32_clockwork.erl b/test/prop_base32_clockwork.erl
new file mode 100644
index 0000000..3df7cb3
--- /dev/null
+++ b/test/prop_base32_clockwork.erl
@@ -0,0 +1,35 @@
+-module(prop_base32_clockwork).
+
+-export([prop_base32_clockwork_encode_decode/1]).
+
+-include_lib("proper/include/proper.hrl").
+
+
+prop_base32_clockwork_encode_decode(doc) ->
+    "base32_clockwork を encode して decode する";
+prop_base32_clockwork_encode_decode(opts) ->
+    [{numtests, 100000}, {on_output, fun proper_output/2}].
+
+
+prop_base32_clockwork_encode_decode() ->
+    ?FORALL(N,
+            range(1, 100),
+            ?FORALL(RandomBytes,
+                    binary(N),
+                    begin
+                        Base32edBytes = base32_clockwork:encode(RandomBytes),
+                        case base32_clockwork:decode(Base32edBytes) of
+                            {ok, RandomBytes} ->
+                                true;
+                            {ok, _} ->
+                                false;
+                            {error, _Reason} ->
+                                false
+                        end
+                    end)).
+
+
+proper_output(".", _Args) ->
+    ok;
+proper_output(Format, Args) ->
+    io:format(Format, Args).