Abstract: [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.