A liquid-cooled-type cooling device includes a casing having a cooling-liquid flow channel. Fins are provided on an inner surface of a top wall of the casing. Each fin has a wavy shape on a horizontal plane perpendicular to a fin height direction. In a left fin of two adjacent fins, lines of intersection between the horizontal plane and right side surfaces of two slant portions connecting two adjacent wave crest portions and a wave trough portion therebetween intersect each other at a first point located on a first straight line. In a right fin, lines of intersection between the horizontal plane and left side surfaces of two slant portions connecting two adjacent wave trough portions and a wave crest portion therebetween intersect each other at a second point located on a second straight line. The first straight line is located on the right fin side of the second straight line.