A display unit in a head mounted display (HMD) is divided into a main body part generating image light; and an emission port part having an emission port through which the generated image light is emitted to the observer's eye. The main body part and the emission port part are connected to each other such that they are allowed to be attached and detached by an external force. In a head mounting state of the HMD, when a first external force acts on the emission port part in response to a situation that the emission port part (e.g., a half mirror) comes into contact with a member located at or near the observing eye or in front of the observing eye within the observer's face and thereby protecting the observing eye, the first external force causes the emission port part to be detached from the main body part.