An electrostatic protection circuit in a semiconductor device includes a first first-conductivity type well extending in a first direction over a semiconductor substrate, a second first-conductivity type well extending in a second direction over the semiconductor substrate and perpendicular to the first direction with one end coupled to a first long side of the first first-conductivity type well, and a second-conductivity type well formed around the first first-conductivity type well and the second first-conductivity type well. It also includes a first high-concentration second-conductivity type region extending in the second direction on a surface of the second first-conductivity type well and a first high-concentration first-conductivity type region extending in the second direction on a surface of the second-conductivity type well while facing the first high-concentration second-conductivity type region.