Abstract: A side release buckle includes: a plug; and a socket, the plug including: a base; a pair of legs; and engaging portions, the socket including: a body; an insertion opening; a housing space; engaged portions; and a pair of guide surfaces. The guide surfaces, which are formed on an inner surface of the housing space and extend in an insertion direction of the legs while being opposed to each other, each include: a squeezing portion formed continuously with corresponding one of the engaged portions; and a guiding portion formed between the squeezing portion and the insertion opening. An interval between the guiding portions near the engaged portions is wider than an interval between the squeezing portions near the engaged portions. An inclination angle of each guiding portion to an insertion direction of the plug is smaller than an inclination angle of each of the squeezing portion to the insertion direction.