An alternating current power supply device comprising: a direct current power supply for generating direct current power; a plurality of parallel direct current to alternating current converters (16a through 16c) electrically connected to the direct current power supply, for converting the direct current power generated by the direct current power supply into alternating current power and supplying the alternating current power to a load; and a controller for controlling operation of the direct current to alternating current converters (16a through 16c); wherein of n (n: a natural number of 2 or greater) direct current to alternating current converters, capacity A(m) of the mth (m: a natural number, 1 ≤ m ≤ n) direct current to alternating current converter is related to rated output W of the direct current power supply by A(m) = 2mW/(n(n + 1)), characterized by a storage unit for storing performance information and operation histories of the direct current to alternating current converters (16a through 16c); and a map for storing combinations of the direct current to alternating current converters (16a through 16c) set beforehand, wherein the controller is configured to detect a demanded load power required by the load and search for the direct current to alternating current converter combination that matches the demanded load power detected, and if there are a plurality of combinations retrieved, the controller is configured to preferentially select, from among the retrieved combinations, one of the combinations which (a) has a higher conversion efficiency for the demanded load power or (b) has a shorter accumulated operating time, compared to the remaining combination(s), and to control the direct current to alternating current converters (16a through 16c). a direct current power supply for generating direct current power; a plurality of parallel direct current to alternating current converters (16a through 16c) electrically connected to the direct current power supply, for converting the direct current power generated by the direct current power supply into alternating current power and supplying the alternating current power to a load; and a controller for controlling operation of the direct current to alternating current converters (16a through 16c); wherein of n (n: a natural number of 2 or greater) direct current to alternating current converters, capacity A(m) of the mth (m: a natural number, 1 ≤ m ≤ n) direct current to alternating current converter is related to rated output W of the direct current power supply by A(m) = 2mW/(n(n + 1)), characterized by a storage unit for storing performance information and operation histories of the direct current to alternating current converters (16a through 16c); and a map for storing combinations of the direct current to alternating current converters (16a through 16c) set beforehand, wherein the controller is configured to detect a demanded load power required by the load and search for the direct current to alternating current converter combination that matches the demanded load power detected, and if there are a plurality of combinations retrieved, the controller is configured to preferentially select, from among the retrieved combinations, one of the combinations which (a) has a higher conversion efficiency for the demanded load power or (b) has a shorter accumulated operating time, compared to the remaining combination(s), and to control the direct current to alternating current converters (16a through 16c).