In an axial flow hydraulic machine, a plural number of grooves 5 are formed on an inner surface of a casing, directed into a pressure gradient direction, for connecting between an inlet side of an impeller 1 and an inside of blade residing region on the casing inner surface. The inputoutput connector includes a connector body and at least one pair of terminals. As a result, when transmission power is low, power loss at the amplitude signal amplifying section is suppressed by DCDC converter, unnecessary operation of DCDC converter is halted when transmission power is high, and power loss can be suppressed regardless of whether transmission power is high or low.