PROBLEM TO BE SOLVED: To provide an AC potential therapy device that can secure a positive and negative peak value ratio of a living body application AC, even if a place of use and usage pattern of an insulating coating conductive mat for applying an AC high voltage to a living body are varied.SOLUTION: One end of a protection combined voltage dividing circuit B1 having a series circuit of a reverse diode D2 and a resistance R2 connected in parallel to a series circuit of a diode D1 and a resistance R1 is connected to a high voltage end P1 of a secondary coil L2 in an AC step-up transformer T. Also, a positive voltage dividing circuit B2 formed by series-connecting a resistance R3 to a diode D3 for this ground end is connected between the other end and a secondary coil ground end P2 of an earth potential. The high voltage AC obtained from a voltage dividing output end b between respective voltage dividing circuits B1 and B2 is fed to an electrically-conductive mat m as a living body application AC. Thereby, even if the living body application AC voltage is varied with variation of the usage pattern of the electrically-conductive mat m, a positive and negative peak value ratio of this AC can be secured to a predetermined ratio, for example, 1 to 3.
