To provide a fin attachment structure capable of facilitating the attachment/detachment of a fin and also of making the attachment of the fin robust, wherein if the fin comes into contact with human body from behind during surfing, the impact of the fin can be eliminated to restrict the damage to the human body to an extreme minimum and thus safety is improved. The above problem can be solved by a fin attachment structure, in which a groove part in which a fin is attached is provided on the bottom surface of a board and further a pin is provided across the groove parts in the nose direction, plungers are provided at the opposing positions on both side surfaces of the groove in the tail direction,wherein the fin has a hook slot that hooks the fin around the pin at the attachment base portion in the nose direction and a recess portion is provided on the fin side surface corresponding to an projection portion of the plunger when the fin is attached, and thereby, the hook slot of the fin is booked around the pin so that the fin can pivot freely and at the same time, the fin is sandwiched and held by the plungers.