To provide bite detection device for a window glass capable of preventing malfunction due to erroneous detection in a condition of high-sensitive bite detection.

By comparison of a pulse period of pulses corresponding the rotation of a driving motor 19 for driving the window glass with an ordinary control threshold, an operating part 12 of a controller 11 temporarily determines the existence of bite, and when bite is temporarily decided, the operating part controls of the drive of the driving motor 19 to reverse in a very small amount. After a very small amount of reversing, the window glass is again operated to close, and by comparison of the pulse period with a low-speed control threshold, the operating part decides the bite when the pulse period exceeds the low- speed control threshold, and reverses the window glass by a designated amount of reversing.