A car cam and locking roller locking structure that opens and closes elevator doors so that the lateral sliding of the car will not affect the opening of the doors. The invention is a mechanism to open and close elevator doors that is used to start the opening and closing operation of car door (1) and boarding entrance door (13) by moving forward end (4a) of car cam (4) furnished for car door (1) forward between a pair of locking rollers (14a) and (14b) furnished for boarding entrance door (13) so that it nearly touches locking roller (14a), while at the same time moving the other locking roller (14b) to grip car cam (4). Step-shaped part (40) is formed in locking roller (14b), and at the same time, catch (50), which catches the step-shaped part (40) to prevent its coming loose, is formed in car cam (4).