A manufacturing method for a chopper circuit that uses soft switching operation includes: identifying devices that constitute the chopper circuit and that are relevant to determining time at which a voltage applied to a main switching element during operation of the chopper circuit takes a minimum value; calculating a design representative value of an observed device that is at least one of the identified devices in such a manner that a plurality of the observed devices are prepared and then variations from a rated value in electrical characteristic of each observed device are subjected to statistical processing; and setting the representative value, instead of the rated value of the electrical characteristic of the observed device, in a switching control unit that controls the timings of switching of the main switching element and an auxiliary switching element on the basis of the electrical characteristics of the identified devices.