An engaging mechanism of a closing device includes an engaging block (10), a positioning hook (12) and a pin (14). The engaging block (10) has a contact surface (16) and a guide surface (18) extending from the contact surface (16). The positioning hook (12) is connected to the engaging block (10) and has a resilient portion (20) and a stop (22) which extends from the resilient portion (20). The stop (22) is located adjacent to the contact surface (16) and located at a distance from the guide surface (18). The pin (14) is located corresponding to the engaging block (10) and slidably contacts the contact surface (16) and the stop (22) of the positioning hook (12). The pin (14) moves over the stop (22) and is disengaged from the contact surface (16) by contacting against the stop (22) and the deformation of the resilient portion (20).
