A head mounted device includes a ring-shaped mount unit for mounting the head mounted device on a head of a user, the ring-shaped mount unit including a first housing having a band portion on each of both sides thereof and a second housing having an engagement portion to be engaged with the band portion, and the ring-shaped mount unit being formed in a ring shape that enables enlargement and reduction of a circumference thereof by engagement of the band portion with the engagement portion. The head mounted device further includes a circumference holding unit, such as a torque limiter, configured to generate a holding force at least in a circumference enlargement direction of the ring-shaped mount unit.