Abstract: A scroll compressor (A) includes a barrier wall (25) which divides the internal cavity of a casing (1) into a discharge chamber (22) and a suction chamber (23) and has a discharge opening (25b) for providing the communication of the compartments (22) and (23), a check valve (27) operable to prevent a flow of gas from the discharge chamber (22) into the suction chamber (23), and a scroll compression mechanism (3) which is provided in the suction chamber (23), which a space (36) left between the mechanism (3) and the barrier wall (25), for discharging compressed gas into the space (36). In addition, a valve (31) is provided in the space (36) which has a seal member (32) operable to interrupt the communication of an inner compartment (34) with an outer compartment (35) of the space (36) during the correct operation period while on the other hand providing the communication during the reverse operation period.