A ventilation member attachable to a housing having an interior space that requires ventilation and an opening for ventilation, the ventilation member comprising: a support having a vent hole serving as a part of an air passage between the interior space and an exterior space of the housing; and an air-permeable membrane disposed on the support to cover one end of the vent hole that opens into the exterior space, wherein the support comprises: a base portion supporting the air-permeable membrane; and a leg portion extending from the base portion toward the interior space and adapted to fix the ventilation member to the opening of the housing, and the leg portion comprises: insertion portions separated from each other in a circumferential direction by slits formed between the insertion portions in an insertion start side of the leg portion, the insertion portions being adapted to be elastically deformed radially inwardly when the insertion portions are inserted into the opening and then to be fixed to the opening; and receding portions each formed in a region between an edge of an inner circumferential surface of the insertion portion and an edge of an outer circumferential surface of the insertion portion at a root of the insertion portion, the receding portion receding from an imaginary circumferential end surface in a direction away from the slit and receding from an imaginary inner circumferential surface toward the outer circumferential surface, the imaginary circumferential end surface being an imaginary end surface including a central axis of the support and a first reference line parallel to the central axis and passing through the edge of the outer circumferential surface, and the imaginary inner circumferential surface being an imaginary surface extending in the circumferential direction from the edge of the inner circumferential surface toward the slit. a support having a vent hole serving as a part of an air passage between the interior space and an exterior space of the housing; and an air-permeable membrane disposed on the support to cover one end of the vent hole that opens into the exterior space, wherein the support comprises: a base portion supporting the air-permeable membrane; and a leg portion extending from the base portion toward the interior space and adapted to fix the ventilation member to the opening of the housing, and a base portion supporting the air-permeable membrane; and a leg portion extending from the base portion toward the interior space and adapted to fix the ventilation member to the opening of the housing, and the leg portion comprises: insertion portions separated from each other in a circumferential direction by slits formed between the insertion portions in an insertion start side of the leg portion, the insertion portions being adapted to be elastically deformed radially inwardly when the insertion portions are inserted into the opening and then to be fixed to the opening; and receding portions each formed in a region between an edge of an inner circumferential surface of the insertion portion and an edge of an outer circumferential surface of the insertion portion at a root of the insertion portion, the receding portion receding from an imaginary circumferential end surface in a direction away from the slit and receding from an imaginary inner circumferential surface toward the outer circumferential surface, the imaginary circumferential end surface being an imaginary end surface including a central axis of the support and a first reference line parallel to the central axis and passing through the edge of the outer circumferential surface, and the imaginary inner circumferential surface being an imaginary surface extending in the circumferential direction from the edge of the inner circumferential surface toward the slit. insertion portions separated from each other in a circumferential direction by slits formed between the insertion portions in an insertion start side of the leg portion, the insertion portions being adapted to be elastically deformed radially inwardly when the insertion portions are inserted into the opening and then to be fixed to the opening; and receding portions each formed in a region between an edge of an inner circumferential surface of the insertion portion and an edge of an outer circumferential surface of the insertion portion at a root of the insertion portion, the receding portion receding from an imaginary circumferential end surface in a direction away from the slit and receding from an imaginary inner circumferential surface toward the outer circumferential surface, the imaginary circumferential end surface being an imaginary end surface including a central axis of the support and a first reference line parallel to the central axis and passing through the edge of the outer circumferential surface, and the imaginary inner circumferential surface being an imaginary surface extending in the circumferential direction from the edge of the inner circumferential surface toward the slit.