There are provided a small-sized power semiconductor module and a small-sized power conversion device capable of reducing ringing voltage. A power semiconductor module includes: a positive electrode-side switching element and a positive electrode-side freewheeling diode corresponding to a positive electrode-side power semiconductor element; a negative electrode-side switching element and a negative electrode-side freewheeling diode corresponding to a negative electrode-side power semiconductor element; a positive electrode conductor pattern; a negative electrode conductor pattern; an AC electrode pattern; and a snubber substrate including an insulating substrate having a snubber circuit formed thereon. The snubber substrate includes the insulating substrate and the at least one snubber circuit arranged on the insulating substrate. The snubber substrate is arranged on at least one of the positive electrode conductor pattern, the negative electrode conductor pattern and the AC electrode pattern.