A bobby pin includes a clamping ribs unit and a hair fork. The clamping rib unit consists of a left and a right clamping rib member interspaced, and the left and the right clamping rib member have a press grip with a shaft hole and a guiding groove. The hair fork has two rods extending from a base member. A shaft stands on the base member, extending in the shaft hole of the press grips with a spring fitted around the shaft. In using, a user presses the two press grips to open the left and the right clamping rib member, with the rods of the hair fork shifted and located in the center of the bobby pin. Then the user inserts the left and the right clamping rib member in hair, with the press grips released to permit the left and the right clamping rib member closed up for clamping hair together with the hair fork.