The present invention relates to a lid locking device for a video cassette having upper and lower cases and a lid mounted on the cases for movement between an open position and a closed position. The lid locking device comprises a lid lock having a pivot for mounting the lid lock within the upper and lower cases for pivotal movement between a lid locking position and a lid releasing position. The device further comprises a rounded groove in the upper side of a spring support member of the lid lock, a square projection on the lid lock comprising a convex portion, and a convex portion of the cassette at a point corresponding to the square projection.
