A rectifier of an automotive alternator includes a heat sink that has fitting holes, in each of which one rectifying element is fitted, and a major surface on which the fitting holes open. The heat sink also has substantially annular ribs, each of which is formed on the major surface around a corresponding one of the fitting holes. Each of the ribs has a first portion, which lies in an area on the major surface where a minimum distance between an inner edge of the heat sink defining the corresponding fitting hole and an outer edge of the heat sink defining an outline of the heat sink is smaller, and a second portion that lies in an area on the major surface where a minimum distance between the inner and outer edges is larger. The first portion has a greater protruding height from the major surface than the second portion.