A power semiconductor module comprising: a plurality of first metal substrates on each of which a power semiconductor device is mounted; a second metal substrate on which a power semiconductor device is not mounted; and an electrically insulating resin package which seals said first metal substrate and said second metal substrate, wherein the plurality of said first metal substrates are separately arranged from each other in the same planar state; said second metal substrate is arranged between said first metal substrates so as to be horizontally arranged in the same planar state as said first metal substrates or to be arranged in different levels by shifting from said first metal substrates; an external connection terminal is extended from each of said first metal substrate and said second metal substrate; when said first metal substrate and said second metal substrate are arranged in the same planar state, the back surface of said first metal substrate on the side opposite to the mounting surface of said power semiconductor device is made to expose outside said electrically insulating resin package to form a first metal substrate side heat dissipation surface and said electrically insulating resin package is protruded from the first metal substrate side heat dissipation surface without exposing the back surface of said second metal substrate; when said first metal substrate and said second metal substrate are arranged in different levels, the back surface of said first metal substrate is made to expose outside said electrically insulating resin package to form a first metal substrate side heat dissipation surface, the outer side surface of said electrically insulating resin package being formed in a protruding shape by covering the back surface of said second metal substrate and being formed in the same planar surface as the first metal substrate side heat dissipation surface, and the outer periphery of the outer side surface on the heat dissipation surface side of said electrically insulating resin package is surrounded by a protruded resin portion which is protruded from the first metal substrate side heat dissipation surface. a plurality of first metal substrates on each of which a power semiconductor device is mounted; a second metal substrate on which a power semiconductor device is not mounted; and an electrically insulating resin package which seals said first metal substrate and said second metal substrate, wherein the plurality of said first metal substrates are separately arranged from each other in the same planar state; said second metal substrate is arranged between said first metal substrates so as to be horizontally arranged in the same planar state as said first metal substrates or to be arranged in different levels by shifting from said first metal substrates; an external connection terminal is extended from each of said first metal substrate and said second metal substrate; when said first metal substrate and said second metal substrate are arranged in the same planar state, the back surface of said first metal substrate on the side opposite to the mounting surface of said power semiconductor device is made to expose outside said electrically insulating resin package to form a first metal substrate side heat dissipation surface and said electrically insulating resin package is protruded from the first metal substrate side heat dissipation surface without exposing the back surface of said second metal substrate; when said first metal substrate and said second metal substrate are arranged in different levels, the back surface of said first metal substrate is made to expose outside said electrically insulating resin package to form a first metal substrate side heat dissipation surface, the outer side surface of said electrically insulating resin package being formed in a protruding shape by covering the back surface of said second metal substrate and being formed in the same planar surface as the first metal substrate side heat dissipation surface, and the outer periphery of the outer side surface on the heat dissipation surface side of said electrically insulating resin package is surrounded by a protruded resin portion which is protruded from the first metal substrate side heat dissipation surface.