A grommet (1, 1A, 1B, 1C, 1D, 1E, 1F) comprising: a body that is formed in an annular shape around a center axis along an axial direction, and is fitted into a through hole, the through hole being formed in an attachment target, along the axial direction to stop water from entering the through hole, a wiring member being inserted through the body along the axial direction; and an umbrella-shaped unit including an annular wall section that extends from the body to a side opposite to a center axis side and is formed in an annular shape around the body, a first lip section that protrudes from the annular wall section toward the attachment target along the axial direction and is formed in an annular shape with a gap on the side opposite to the center axis side of the body, and a second lip section that protrudes from the annular wall section toward the attachment target along the axial direction and is formed in an annular shape with a gap on the side opposite to the center axis side of the first lip section, the first lip section and the second lip section abutting an abutting target surface provided on the attachment target in a state in which the body is fitted into the through hole, wherein the first lip section and the second lip section are provided in the annular wall section so as to be located within an installation region of an insulator provided around the through hole of the attachment target to surround the through hole when viewed along the axial direction, and the umbrella-shaped unit includes a stress concentration section that is provided in an annular shape in the annular wall section on the center axis side with respect to the first lip section, is located within the installation region when viewed along the axial direction, and is bendable when receiving concentrated stress in a state in which the body is fitted into the through hole and the first lip section and the second lip section abut the abutting target surface, characterized in that the stress concentration section is located on the center axis side with respect to the first lip section in the annular wall section, and is located in an area separated from a proximal end of the annular wall section on a side of the body toward a side of the first lip section along an extension direction of the annular wall section by 1/3 or more of a length between the proximal end and the first lip section. a body that is formed in an annular shape around a center axis along an axial direction, and is fitted into a through hole, the through hole being formed in an attachment target, along the axial direction to stop water from entering the through hole, a wiring member being inserted through the body along the axial direction; and an umbrella-shaped unit including an annular wall section that extends from the body to a side opposite to a center axis side and is formed in an annular shape around the body, a first lip section that protrudes from the annular wall section toward the attachment target along the axial direction and is formed in an annular shape with a gap on the side opposite to the center axis side of the body, and a second lip section that protrudes from the annular wall section toward the attachment target along the axial direction and is formed in an annular shape with a gap on the side opposite to the center axis side of the first lip section, the first lip section and the second lip section abutting an abutting target surface provided on the attachment target in a state in which the body is fitted into the through hole, wherein the first lip section and the second lip section are provided in the annular wall section so as to be located within an installation region of an insulator provided around the through hole of the attachment target to surround the through hole when viewed along the axial direction, and the umbrella-shaped unit includes a stress concentration section that is provided in an annular shape in the annular wall section on the center axis side with respect to the first lip section, is located within the installation region when viewed along the axial direction, and is bendable when receiving concentrated stress in a state in which the body is fitted into the through hole and the first lip section and the second lip section abut the abutting target surface, characterized in that the stress concentration section is located on the center axis side with respect to the first lip section in the annular wall section, and is located in an area separated from a proximal end of the annular wall section on a side of the body toward a side of the first lip section along an extension direction of the annular wall section by 1/3 or more of a length between the proximal end and the first lip section.