A rotor of a brushless motor used in a fuel pump includes a permanent magnet having first and second ends that are configured to have a thickness ratio so that a degree of margin of those ends, which is a difference between an allowable stress and a temperature stress due to expansion and contraction of a rotor core caused by a temperature change is equal to or greater than a preset value. As a result, a cracking of the permanent magnet on the both ends that is caused by repeated expansions and contractions of the rotor core is prevented.