A buckle of the invention is formed of a hollow female member, which is provided with an inserting hole and first engaging portions, and a male member provided with a collar portion and elastic pieces disposed at both end portions of a front surface of the collar portion. Each of the elastic pieces includes a second engaging portion at a distal end thereof, and the elastic pieces are disposed to face each other and inserted into the inserting hole of the female member. The both end portions of the front surface of the collar portion are respectively provided with concave portions, so that the collar portion and the elastic pieces are overlapped in a longitudinal direction thereof. Accordingly, an entire length of the male member is shortened while a length of the elastic piece and bending margin are obtained as required. Thus, the entire length of the buckle formed by connecting the female member and the male member does not become too long relative to the width thereof to thereby match the balance between the length and the width of the buckle.