A contact lens (10, 52, 54, 62) having a convex lens front surface and a concave lens rear surface while being provided with an optical part in its center portion and a peripheral part around the optical part: the peripheral part is provided with at least one thick portion (32, 58) and at least one thin portion (30, 56) away from each other in a circumferential direction which exhibit a positioning effect in the circumferential direction in a worn state; in a changing region (34, 60) provided between the thick and thin portions (30, 32, 56, 58) in the peripheral part where a thickness dimension of the lens (10, 52, 54, 62) changes in the circumferential direction, the lens front surface is given a front thickness change so as to get closer to the lens rear surface from the thick portion (32, 58) toward the thin portion (30, 56) in the circumferential direction, while the lens rear surface is given a rear thickness change so as to get closer to the lens front surface from the thick portion (32, 58) toward the thin portion (30, 56) in the circumferential direction, the lens front and rear surfaces (18, 20) in the changing region (34, 60) slope in a direction of getting closer to each other from the thick portion (32, 58) toward the thin portion (30, 56) in the circumferential direction so that the difference between the thickness dimension of the thin portion (30, 56) and the thickness dimension of the thick portion (32, 58) is shared between the lens front and rear surfaces (18, 20), wherein the lens front and rear surfaces (18, 20) in the changing region (34, 60) have the rates of front and rear thickness changes gradually reduced to zero at both ends in the circumferential direction connecting to the thin portion and the thick portion, the contact lens (10, 52, 54, 62) being characterized in that: the at least one thick portion comprises a pair of thick portions provided on left and right sides of the lens (10, 52) in the worn state, and the at least one thin portion comprises a pair of thin portions provided on upper and lower sides of the lens (10, 52) in the worn state. the peripheral part is provided with at least one thick portion (32, 58) and at least one thin portion (30, 56) away from each other in a circumferential direction which exhibit a positioning effect in the circumferential direction in a worn state; in a changing region (34, 60) provided between the thick and thin portions (30, 32, 56, 58) in the peripheral part where a thickness dimension of the lens (10, 52, 54, 62) changes in the circumferential direction, the lens front surface is given a front thickness change so as to get closer to the lens rear surface from the thick portion (32, 58) toward the thin portion (30, 56) in the circumferential direction, while the lens rear surface is given a rear thickness change so as to get closer to the lens front surface from the thick portion (32, 58) toward the thin portion (30, 56) in the circumferential direction, the lens front and rear surfaces (18, 20) in the changing region (34, 60) slope in a direction of getting closer to each other from the thick portion (32, 58) toward the thin portion (30, 56) in the circumferential direction so that the difference between the thickness dimension of the thin portion (30, 56) and the thickness dimension of the thick portion (32, 58) is shared between the lens front and rear surfaces (18, 20), wherein the lens front and rear surfaces (18, 20) in the changing region (34, 60) have the rates of front and rear thickness changes gradually reduced to zero at both ends in the circumferential direction connecting to the thin portion and the thick portion, the contact lens (10, 52, 54, 62) being characterized in that: the at least one thick portion comprises a pair of thick portions provided on left and right sides of the lens (10, 52) in the worn state, and the at least one thin portion comprises a pair of thin portions provided on upper and lower sides of the lens (10, 52) in the worn state. the at least one thick portion comprises a pair of thick portions provided on left and right sides of the lens (10, 52) in the worn state, and the at least one thin portion comprises a pair of thin portions provided on upper and lower sides of the lens (10, 52) in the worn state.