PURPOSE: To prevent a door from being excessively opened by providing a cushion bar made of a resilient material, a shield fixed to the cushion bar and cam plates slid in the longitudinal direction in a door closer body.

CONSTITUTION: This back checking means is constituted of a pad-shaped cushion bar 62 fitted to the rear wall 16 of a housing 12 and made of a resilient material and a metallic shield 64 covered on the cushion bar 62 on the opposite side to a rear wall 16 and fixed by rivets. Cam plates 35, 36 are set to engage the shield 64 approximately 4° prior to a normal full open position of a door. When the door is continuously opened, plates 35, 36 are continuously moved backward, the cushion bar 62 is compressed to increase the resistance against further opening, and the door can be prevented from being opened to the last approximately 4° or further.