A cutting tool of an aspect is provided with a holder and a cutting insert attached to an insert pocket of the holder. The cutting insert includes a front end surface, a rear end surface, a front side surface, a rear side surface, an outer side surface, and an inner side surface. The cutting edge is disposed along a ridge line at an intersection between the front side surface and the front end surface, and a ridge line at an intersection between the front side surface and the outer side surface. The insert pocket includes a restraining surface that is in contact with the rear side surface, in a front end view, the restraining surface includes a projecting portion having a curved line shape projecting toward the front in the rotational direction, and the rear side surface includes a recessed portion that is in contact with the projecting portion.