diff --git a/bbs/gcaptcha/gcaptcha.lib.php b/bbs/gcaptcha/gcaptcha.lib.php
index 9eb3fcc05..a1b9af3a2 100644
--- a/bbs/gcaptcha/gcaptcha.lib.php
+++ b/bbs/gcaptcha/gcaptcha.lib.php
@@ -179,7 +179,7 @@ function captcha_html($class='captcha')
     $html .= PHP_EOL.'<script src="'.G4_GCAPTCHA_URL.'/gcaptcha.js"></script>'; 
     $html .= '<fieldset id="captcha" class="'.$class.'">';
     $html .= '<legend class="sound_only">자동등록방지</legend>';
-    $html .= '<img src="'.$jpg_file_url.'" alt="자동등록방지 숫자">';
+    $html .= '<img src="'.$jpg_file_url.'?_='.rand().'" alt="자동등록방지 숫자">';
     $html .= '<a href="'.$wav_file_url.'" id="captcha_wav" target="_blank"><img src="'.G4_GCAPTCHA_URL.'/img/sound.gif" alt="숫자를 음성으로 듣기"></a>';
     $html .= '<input type="text" id="captcha_key" name="captcha_key" class="captcha_box frm_input" size="6" maxlength="6" required title="자동등록방지 숫자 입력">';
     $html .= '<p class="sound_only">자동등록방지 숫자를 순서대로 입력하세요.</p>';