[Problem] The present invention relates to a surfboard fin attachment structure. More specifically, the invention addresses the problem of providing a surfboard fin attachment structure, which is capable of detachably attaching a fin to a surfboard, wherein the attachment structure is capable of tight fitting even though easy attachment and detachment are possible and allows fitting without fin shaking or shuddering. [Solution] A surfboard fin attachment structure comprising: pin insertion recesses on both side surfaces of a cavity and, continuous therewith, grooves that continue in the depth direction of the cavity, said grooves extending from a given depth towards the back of the direction of board movement in the longitudinal direction of the fin box; and, on both sides of the fin attachment base, pins corresponding to the pin insertion recesses. The fin is attached by aligning the pins with the pin insertion recesses and inserting the attachment base, and after insertion, moving the fin towards the back of the direction of board movement.