A simple crime prevention alarm device for the windows of dwelling houses or the like. The alarm device can be simply and easily attached to and placed on various kinds of objects, such as windows or the like, to prevent crime. The manufacturing cost and the attachment cost are reduced, and further provide a simple alarm device which can be used as an urgent call means. A simple crime prevention alarm device for windows according to this invention comprises a casing, and the casing houses therein a reel for taking up a string, a coil spring for giving a force of taking up the string around the reel, a switching-on projection means operation switch when the reel is rotated by the pulling-out of the string or the pulling-in of the string due to the coil spring, an alarm operation switch adapted to be turned on when the switching-on projection means has kicked the switch by the pulling-out of the string or the pulling-in of the string due to the coil spring, an alarm sound generating device which is operated by the alarm operation switch, and a battery which serves to give power to the alarm sound generating device. The string is provided at a free end thereof with a fixing means which can be secured to a window frame, while the casing comprises an attachment means for attaching the casing itself.