A switching type power source device used for magnetic field generation coils for an MRI device in which a switching power sources (9˜11) are constituted by a first and a second multi level PWM inverter (12,13) having a same number of potential levels connected in parallel each other with respect to magnetic field generating coils (6˜8) for the MRI device working as a load as well as a switching control circuit (19) for drive controlling the first and the second multi level PWM inverter (12,13) is constituted to drive control the first and the second multi level PWM inverter (12,13) in a manner to shift the switching phases thereof each other, thereby, ripple components in currents output from the first and the second multi level PWM inverter (12,13) are canceled out each other and a current with a further reduced ripple components as a whole can be supplied to the load (6˜8).