A cutting tool includes a main body. The main body includes a distal end surface, a rear end surface, and a side surface. A spiral first groove and a spiral second groove are formed on the side surface of the main body. The first groove has at least four installation surfaces. The first installation surface is located on a most rear end surface side. The second installation surface is located closer to a distal end surface side with respect to the first installation surface. A length from the first installation surface to the second groove in a circumferential direction along the rotation direction of the main body is set to a first length. A length from the second installation surface to the second groove in the circumferential direction is set to a second length. The first length is longer than the second length.