An expander-compressor unit (200) includes a closed casing (1), a compression mechanism (2), an expansion mechanism (3), a shaft (5), and an oil pump (6). The shaft (5) includes an upper shaft (5s) provided with an upper eccentric portion (5a) for the compression mechanism (2), and a lower shaft (5t) provided with lower eccentric portions (5d and 5c) for the expansion mechanism (3) and an intermediate eccentric portion (5e) for the oil pump (6). The expansion mechanism (3) has an upper bearing member (45) for supporting a supported portion (5f) of the lower shaft (5t) located immediately above the lower eccentric portion (5d). The intermediate eccentric portion (5e) has a diameter equal to or less than that of the supported portion (5f).