To provide an operation device for use by a user by holding in one hand, comprising a thumb operating area defined on a surface of the enclosure of the operation device, where an operation member to be operated by the user, using his/her thumb, while holding the operation device is provided; an inclination operation member including a stick part projecting from the thumb operating area, for being operated by the user by inclining the stick part, using the thumb; and an operation button provided on the surface of the enclosure in a position opposed to the thumb operating area, being capable of being pressed by the user, using another finger, in a direction intersecting a direction toward the inclination operation member.