A lock mechanism for a stage apparatus, includes a stationary support board; a movable stage; a leaf spring supported by the stationary support board; a press portion and a pressed portion provided on the leaf spring and the movable stage, respectively, a frictional contacting member being fixed to at least one of opposed surfaces of the press portion and the pressed portion; an electromagnet for resiliently deforming the leaf spring in a lock releasing direction to disengage the frictional contacting member from the one of opposed surfaces of the press portion and the pressed portion; and a permanent magnet, fixed to the stationary support board, which magnetically attracts the leaf spring to hold the frictional contacting member and the one of opposed surfaces of the press portion and the pressed portion in a disengaged state when the leaf spring is resiliently deformed by the electromagnet.