A quick release structure for a bicycle comprises a positioning post and an engaging member. The positioning post and the engaging member are disposed on the two tubes of the bicycle, respectively. The positioning post includes a stopping block and a spring. When the positioning post is inserted into the engaging member, the stopping block can be used together with the spring to restrict the positioning post in the engaging member, so that the two tubes of the bicycle can be assembled. When the stopping block is pressed, the positioning post can disengage from the engaging member. Hence, the quick release structure for a bicycle can be quickly assembled and disassembled.