A heat energy recovery apparatus include a compressor which has a piston for compressing sucked-in working gas; a heat exchanger which makes the working gas compressed by the compressor absorb heat of high temperature fluid; an expander which has a piston to be moved under pressure by expansion of the heat-absorbed working gas; and an accumulator which stores the working gas compressed by the compressor when required output is low or heat receiving capacity of the working gas is small. The apparatus preferably include a blocking unit which blocks discharge of the working gas from the expander when the heat receiving capacity of the working gas is small and the compressed working gas to the accumulator is being stored.