To provide a switching mode power conversion apparatus that facilitates design while being loyal to electromagnetics, and has a high efficiency of power conversion at a high repetition frequency exceeding 1 MHz and has a superior electromagnetic compatibility.

The solitary electromagnetic wave concept is employed in designing this switching mode power conversion apparatus. In a back converter, a lossy transmission line 60 is connected to the power reception side of a MOSFET 64 and a lossy transmission line 63 is connected to the power transmission side of the MOSFET 64, and a low-impedance lossy transmission line 55 is connected between the lossy transmission line 60 and a DC power supply 4 and a reactor 74 is connected to the load side of the lossy transmission line 63. Solitary electromagnetic waves excited by the MOSFET 64 attenuate much on the lossy transmission lines 60 and 63, but the reactor 74 is applied with a DC supply voltage at the rise time of the MOSFET 64 and so the back converter works normally. The solitary electromagnetic waves attenuate even in the low-impedance lossy transmission line 55, thereby unwanted electromagnetic waves from the back converter are virtually completely suppressed.