A grommet which is configured to cover a periphery of a wire harness includes a panel mounting portion which is configured to be mounted to a panel. The panel mounting portion includes a base portion which is formed in an annular shape, a seal portion which is formed on the base portion and is configured to be in close contact with a surface of the panel, and a groove portion which is formed between the base portion and the seal portion along a peripheral direction of the panel mounting portion. A plurality of reinforcing ribs are configured to connect the base portion and the seal portion and are arranged in the peripheral direction in the groove portion, and the reinforcing ribs are inclined with respect to a mounting direction of the panel mounting portion to the panel.