A connector, comprising: a housing connectable to a mating housing; and a seal member mounted in the housing and configured to be held in close contact with the two housings (11, 51) in a connected state by being sandwiched between the two housings (11, 51); wherein: the housing is formed with at least one catching piece; an end surface of the seal member serves as a pressing surface; the pressing surface is pressed to push the seal member to a mount position in the process of mounting the seal member into the housing and the seal member resiliently moves past the catching piece and is engaged with the catching piece at the mount position; and the seal member includes an annular seal main body and a flange portion projecting radially outwardly from the seal main body and extending in a circumferential direction along the seal main body; wherein a pair of pressing surfaces of the seal member are formed at opposite end portions of the flange portion in the circumferential direction; characterized in that the pressing surfaces of the seal member are arranged at a positions at least partly overlapping the catching piece in a projecting direction of the catching piece when the seal member is mounted into the housing. a housing connectable to a mating housing; and a seal member mounted in the housing and configured to be held in close contact with the two housings (11, 51) in a connected state by being sandwiched between the two housings (11, 51); wherein: the housing is formed with at least one catching piece; an end surface of the seal member serves as a pressing surface; the pressing surface is pressed to push the seal member to a mount position in the process of mounting the seal member into the housing and the seal member resiliently moves past the catching piece and is engaged with the catching piece at the mount position; and the seal member includes an annular seal main body and a flange portion projecting radially outwardly from the seal main body and extending in a circumferential direction along the seal main body; wherein a pair of pressing surfaces of the seal member are formed at opposite end portions of the flange portion in the circumferential direction; characterized in that the pressing surfaces of the seal member are arranged at a positions at least partly overlapping the catching piece in a projecting direction of the catching piece when the seal member is mounted into the housing. the housing is formed with at least one catching piece; an end surface of the seal member serves as a pressing surface; the pressing surface is pressed to push the seal member to a mount position in the process of mounting the seal member into the housing and the seal member resiliently moves past the catching piece and is engaged with the catching piece at the mount position; and the seal member includes an annular seal main body and a flange portion projecting radially outwardly from the seal main body and extending in a circumferential direction along the seal main body; wherein a pair of pressing surfaces of the seal member are formed at opposite end portions of the flange portion in the circumferential direction; characterized in that the pressing surfaces of the seal member are arranged at a positions at least partly overlapping the catching piece in a projecting direction of the catching piece when the seal member is mounted into the housing.