A superjunction semiconductor device comprising: a drift layer serving as a parallel pn layer in which a first-conductivity-type semiconductor region and a second-conductivity-type semiconductor region extending in a direction perpendicular to a main surface of a first-conductivity-type semiconductor substrate with a high impurity concentration are alternately arranged at a pitch in a direction parallel to the main surface of the semiconductor substrate so as to be adjacent to each other; an active region that serves as a main current path, wherein in the active region a pitch between the first-conductivity type semiconductor region and the second-conductivity-type semiconductor region of the parallel pn layer is a first pitch; a temperature detection region which is provided in the active region and wherein in the temperature detection region a pitch between the first-conductivity-type semiconductor region and the second-conductivity-type semiconductor region of the parallel pn layer is less than the first pitch; a first-conductivity-type semiconductor layer that is provided above a surface of the parallel pn layer in the temperature detection region with an insulating film interposed therebetween; a second-conductivity-type semiconductor layer that is provided above the surface of the parallel pn layer in the temperature detection region with the insulating film interposed therebetween and is arranged so as to come into contact with the first-conductivity-type semiconductor layer to form a pn junction; and a temperature detecting device that is a semiconductor layer including the first-conductivity-type semiconductor layer and the second-conductivity-type semiconductor layer, wherein a current flows to the first-conductivity-type semiconductor region in an on-state of the superjunction semiconductor device and the parallel pn layer is depleted in an off-state of the superjunction semiconductor device to sustain a reverse blocking voltage. a drift layer serving as a parallel pn layer in which a first-conductivity-type semiconductor region and a second-conductivity-type semiconductor region extending in a direction perpendicular to a main surface of a first-conductivity-type semiconductor substrate with a high impurity concentration are alternately arranged at a pitch in a direction parallel to the main surface of the semiconductor substrate so as to be adjacent to each other; an active region that serves as a main current path, wherein in the active region a pitch between the first-conductivity type semiconductor region and the second-conductivity-type semiconductor region of the parallel pn layer is a first pitch; a temperature detection region which is provided in the active region and wherein in the temperature detection region a pitch between the first-conductivity-type semiconductor region and the second-conductivity-type semiconductor region of the parallel pn layer is less than the first pitch; a first-conductivity-type semiconductor layer that is provided above a surface of the parallel pn layer in the temperature detection region with an insulating film interposed therebetween; a second-conductivity-type semiconductor layer that is provided above the surface of the parallel pn layer in the temperature detection region with the insulating film interposed therebetween and is arranged so as to come into contact with the first-conductivity-type semiconductor layer to form a pn junction; and a temperature detecting device that is a semiconductor layer including the first-conductivity-type semiconductor layer and the second-conductivity-type semiconductor layer, wherein a current flows to the first-conductivity-type semiconductor region in an on-state of the superjunction semiconductor device and the parallel pn layer is depleted in an off-state of the superjunction semiconductor device to sustain a reverse blocking voltage.