Disclosed is an expander-integrated compressor (100) including a compression mechanism (2) for compressing a working fluid, an expansion mechanism (3) for expanding the working fluid, and a shaft (5) for coupling the compression mechanism (2) to the expansion mechanism (3). The expansion mechanism (3) comprises a variable vane mechanism (60). Taking the period that a first vane (48) is in contactwith a first piston (46) and the period that the first vane (48) is separated from the first piston (46) during the period of a single rotation of the shaft (5) as P1 and P2 respectively, the variable vane mechanism (60) controls the movement of the first vane (48) in such a way as to enable the ratio (P2/P1) of the period P2 to the period P1 to be adjusted.