An electronic pen includes a casing, an opening portion formed on one side of the casing, a core body that projects outside of the casing through the opening portion, a circuit board, and a core body insertion member disposed in the casing and having a hollow space that houses the core body. The hollow space includes a hollow portion between the core body insertion member and the core body when the core body insertion member houses the core body, the hollow portion communicating, via the opening portion, with a first space external to the electronic pen, and the hollow portion separated from a second space in which the circuit board is disposed.