A semiconductor device includes: a substrate (10); a semiconductor layer (20) disposed on a main surface of this substrate (10); and a first main electrode (30) and a second main electrode (40), which are disposed on the substrate (10) separately from each other with the semiconductor layer (20) sandwiched therebetween and are individually end portions of a current path of a main current flowing in an on-state. The semiconductor layer (20) includes: a first conductivity-type drift region (21) through which a main current flows; a second conductivity-type column region (22) that is disposed inside the drift region (21) and extends in parallel to a current path; and an electric field relaxation region (23) that is disposed in at least a part between the drift region (21) and the column region (22) and is either a low-concentration region in which an impurity concentration is lower than in the same conductivity-type adjacent region or a non-doped region.