A port-equipped bag (1) comprises a bag body (3) formed in a bag shape from a sheet, and a cylindrical port member (2) attached to the bag body (3). The port member (2) can be fitted with an inner plug (50) and a cap (4). The port member (2) has a fitting part (25) covered by the cap (4) when the cap (4) is fitted, and an annular lip (26) protruding towards the outer side of the port member (2). The lip (26) has an annular engagement surface (26A) facing a side of the bag body (3). In a cross-section along the axial direction of the fitting part (25), the engagement surface (26A) is disposed at 45135° with respect to the outer peripheral surface of the fitting part (25).
