elements includes one power circuit unit which is described below the casing 1 includes a bottom cover 12 made of sheet metal and a top cover 13 made of sheet metal which are assembled into a flat box shape and a front panel 14 made of resin which is provided in a front end of the bottom cover 12 and the top cover 13 a top plate 15 of the casing 1 is formed by a top plate of the top cover 13 and left and right side plates 16 of the casing 1 are formed by a mating structure of side plates of the top cover 13 and the bottom cover 12 a back plate 17 of the casing 1 is formed by a back plate of the bottom cover 12 and a bottom plate not shown of the casing 1 is formed by a bottom plate of the bottom cover 12 reference numeral 21 denotes a fan and 22 denotes a terminal group as shown in fig1 a power circuit unit 3 includes a wiring board 31 as a power board on which a line filter 32 and a transformer 34 as electric components and a capacitor and a radiator plate as tall components not shown are mounted the line filter 32 and the transformer 34 are included in a primary circuit and the capacitor and the like are included in a primary power circuit the power circuit unit 3 is fixed to the bottom plate of the casing 1 by means of a plurality.