A scroll compressor comprising: a compression mechanism that includes a movable scroll and a fixed scroll and has a compression chamber defined between the movable scroll and the fixed scroll , wherein the compression mechanism has a back-pressure chamber defined on a back face of an end plate of the movable scroll , the compression mechanism has an annular space defined at an outer periphery of the end plate of the movable scroll , the movable scroll has a movable-side passage through which the compression chamber intermittently communicates with the back-pressure chamber in accordance with eccentric rotation of the movable scroll , and the end plate of the movable scroll has a communication space through which the movable-side passage communicates with the annular space characterized in that the communication space includes: a first communication portion (C1) located forward of the movable-side passage in a direction of eccentric rotation; and a second communication portion (C2) located rearward of the movable-side passage in the direction of eccentric rotation, and a circumferential width W1 of an opening in the first communication portion (C1), the opening being open toward to the annular space , is larger than a circumferential width W2 of an opening in the second communication portion (C2), the opening being open toward the annular space . a compression mechanism that includes a movable scroll and a fixed scroll and has a compression chamber defined between the movable scroll and the fixed scroll , wherein the compression mechanism has a back-pressure chamber defined on a back face of an end plate of the movable scroll , the compression mechanism has an annular space defined at an outer periphery of the end plate of the movable scroll , the movable scroll has a movable-side passage through which the compression chamber intermittently communicates with the back-pressure chamber in accordance with eccentric rotation of the movable scroll , and the end plate of the movable scroll has a communication space through which the movable-side passage communicates with the annular space characterized in that the communication space includes: a first communication portion (C1) located forward of the movable-side passage in a direction of eccentric rotation; and a second communication portion (C2) located rearward of the movable-side passage in the direction of eccentric rotation, and a circumferential width W1 of an opening in the first communication portion (C1), the opening being open toward to the annular space , is larger than a circumferential width W2 of an opening in the second communication portion (C2), the opening being open toward the annular space . a first communication portion (C1) located forward of the movable-side passage in a direction of eccentric rotation; and a second communication portion (C2) located rearward of the movable-side passage in the direction of eccentric rotation, and a circumferential width W1 of an opening in the first communication portion (C1), the opening being open toward to the annular space , is larger than a circumferential width W2 of an opening in the second communication portion (C2), the opening being open toward the annular space . <EOS>