A power supply device (100-1) includes: a substrate (20) on which an electric component (25) is mounted; a chassis (10) including a chassis surface (11) to be a surface facing one surface (20a) of the substrate (20); and cured insulating resin (27-1) to be placed between the one surface (20a) of the substrate (20) and the chassis surface (11) so as to be connected to the one surface (20a) and the chassis surface (11), the cured insulating resin (27-1) having a thermal conductivity between 1 W/mK and 10 W/mK inclusive.