Abstract: A safety device for an automatic window opening and closing mechanism which includes a first detector for detecting a foreign object caught in the window, when the relative velocity decrease detected by a first relative velocity detector is greater than a first reference value, with the window in a safety control range; and a second velocity detector to detect a yielding foreign object caught in the window. When a plurality of successive changes in closing velocity of the window are detected and the sum of the changes calculated by calculator is greater than a second reference value, a release instruction is given to the motor driving circuit based on the detection result of the first or second detecting means to stop or drive the motor in an opening direction, thereby ensuring stable detection of the foreign object, even if it is soft, and to prevent the foreign object from being caught in the window.