An electronic pen includes a first casing, a second casing disposed within the first casing, and an electronic pen main body unit incorporating an electronic pen function disposed within the second casing, in which the electronic pen main body unit includes a side switch unit having an operating element exposed on a side surface of the second casing, and an operating opening portion is disposed in a side surface of the first casing, and the operating opening portion exposes the operating element exposed on the side surface of the second casing.