A swimming assistance apparatus comprising: a body made of a material which floats on water or formed in a hollow tube type which floats on water; a first fitting hole and a second fitting hole each formed in a hollow cylinder shape and penetrating through the body to surround a part of a user's lower body; and a cut part formed in the wall of one side of each of the fitting holes in a longitudinal direction of the fitting holes in such a way that a part of the user's lower body can be inserted into each of the fitting holes, wherein when the user swims in a state where the user's lower body is inserted into each of the fitting holes, the user's lower body floats on water by buoyancy of the body, wherein each of the fitting holes is configured in such a manner that the user can insert the right and left legs into the first and second fitting holes respectively and each of the first and second fitting holes includes the cut part, and wherein the swimming assistance apparatus further comprises, a depressed part respectively defined on each of the upper and lower sides of the body for decreasing underwater resistance, each of the depressed parts being inwardly depressed to a specific depth between the first fitting hole and the second fitting hole of the body, characterized in that each of the depressed parts is extended in the longitudinal direction of the fitting hole and has a contour defined as a curved surface along the first and second fitting holes, and the width between the curved surfaces of the contour of the depressed parts between the first and second fitting holes gradually narrows in inward direction. a body made of a material which floats on water or formed in a hollow tube type which floats on water; a first fitting hole and a second fitting hole each formed in a hollow cylinder shape and penetrating through the body to surround a part of a user's lower body; and a cut part formed in the wall of one side of each of the fitting holes in a longitudinal direction of the fitting holes in such a way that a part of the user's lower body can be inserted into each of the fitting holes, wherein when the user swims in a state where the user's lower body is inserted into each of the fitting holes, the user's lower body floats on water by buoyancy of the body, wherein each of the fitting holes is configured in such a manner that the user can insert the right and left legs into the first and second fitting holes respectively and each of the first and second fitting holes includes the cut part, and wherein the swimming assistance apparatus further comprises, a depressed part respectively defined on each of the upper and lower sides of the body for decreasing underwater resistance, each of the depressed parts being inwardly depressed to a specific depth between the first fitting hole and the second fitting hole of the body, characterized in that each of the depressed parts is extended in the longitudinal direction of the fitting hole and has a contour defined as a curved surface along the first and second fitting holes, and the width between the curved surfaces of the contour of the depressed parts between the first and second fitting holes gradually narrows in inward direction.