In a multiple output multiple step-up rectifier circuit of the invention, an output voltage of a power source circuit is supplied to a plurality of Crockroft-Walton multiple step-up rectifier circuits connected in parallel with each other. The capacitor capacitance ratio of the rectifier circuits is proportional to the ratio of the numbers of multiplication stages of respective rectifier circuits. Particularly, when the squares of the number of multiplication stages is comparatively large, the capacitor capacitance ratio is set to be proportional to n1.sup.2 /n2.sup.2 where n1 and n2 are the numbers of multiplication stages of two rectifier circuits of the plurality of rectifier circuits. When the number of multiplication stages is small, the capacitor capacitance ratio is set to be proportional to:(2n1.sup.2 /3+n1/2-1/6)/(2n2.sup.2 /3+n2/2-1/6).The power source circuit can change its output voltage such that the output of any of the plurality of rectifier circuits is the same in the non-load and load states.