A connector comprising: a housing configured to be fitted to a counterpart member and having a fitting portion; and a seal member configured to be attached to the fitting portion of the housing, wherein the housing includes a groove portion; wherein the groove portion is configured such that the seal member is attached to the groove portion, the groove portion extending continuously over a circumferential direction of the housing, opening outward in a radial direction of the housing and having a bottom surface, a first side wall provided in a first direction in which the housing is fitted to the counterpart member and a second side wall provided in a second direction being opposite to the first direction, characterized in that the housing includes at least one protruding portion that extends from the second side wall toward the first side wall and has an end surface facing the first side wall; at least a part of the end surface has an inclined surface inclined such that an outer end of the inclined surface in the radial direction is closer to the first side wall than an inner end of the inclined surface in the radial direction; the seal member includes: an engaging portion configured to, when the seal member is attached to the groove portion, engage with the at least one protruding portion; and a side surface configured to, when the seal member is attached to the groove portion, face the end surface of the protruding portion; the engaging portion and the protruding portion are configured to be engaged with each other and to prevent the seal member from moving in the circumferential direction with respect to the housing; and wherein a first distance between the outer end of the inclined surface in the radial direction and the bottom surface is greater than a second distance between the bottom surface and an outer end of the side surface of the seal member in the radial direction. a housing configured to be fitted to a counterpart member and having a fitting portion; and a seal member configured to be attached to the fitting portion of the housing, wherein the housing includes a groove portion; wherein the groove portion is configured such that the seal member is attached to the groove portion, the groove portion extending continuously over a circumferential direction of the housing, opening outward in a radial direction of the housing and having a bottom surface, a first side wall provided in a first direction in which the housing is fitted to the counterpart member and a second side wall provided in a second direction being opposite to the first direction, characterized in that the housing includes at least one protruding portion that extends from the second side wall toward the first side wall and has an end surface facing the first side wall; at least a part of the end surface has an inclined surface inclined such that an outer end of the inclined surface in the radial direction is closer to the first side wall than an inner end of the inclined surface in the radial direction; the seal member includes: an engaging portion configured to, when the seal member is attached to the groove portion, engage with the at least one protruding portion; and a side surface configured to, when the seal member is attached to the groove portion, face the end surface of the protruding portion; the engaging portion and the protruding portion are configured to be engaged with each other and to prevent the seal member from moving in the circumferential direction with respect to the housing; and wherein a first distance between the outer end of the inclined surface in the radial direction and the bottom surface is greater than a second distance between the bottom surface and an outer end of the side surface of the seal member in the radial direction.