An optical device in which a light emitted from an image formation device is incident, guided, and emitted, the optical device comprising a first light guide plate and a second light guide plate, and a first deflection unit provided on the first light guide plate and a second deflection unit provided on the second light guide plate, wherein the first deflection unit includes a first A deflection member, a first B deflection member, and a first C deflection member, the second deflection unit includes a second A deflection member, a second B deflection member, and a second C deflection member, a part of the light emitted from the image formation device is incident on the first A deflection member, a light incident on the first A deflection member is deflected by the first A deflection member, totally reflected inside the first light guide plate and incident on the first B deflection member, deflected by the first B deflection member, totally reflected inside the first light guide plate and incident on the first C deflection member, deflected by the first C deflection member, and emitted toward a pupil of an observer, at least a rest of the light emitted from the image formation device is incident on the second A deflection member, a light incident on the second A deflection member is deflected by the second A deflection member, totally reflected inside the second light guide plate, incident on the second B deflection member, deflected by the second B deflection member, totally reflected inside the second light guide plate, incident on the second C deflection member, deflected by the second C deflection member, and emitted toward the pupil of the observer, and when a direction in which a propagation direction of a light deflected by the first B deflection member in the first light guide plate is orthogonally projected onto the first light guide plate is a first direction, and a direction in which a propagation direction of a light deflected by the second B deflection member in the second light guide plate is orthogonally projected onto the first light guide plate is a second direction, the first direction is opposite to the second direction. wherein the first deflection unit includes a first A deflection member, a first B deflection member, and a first C deflection member, the second deflection unit includes a second A deflection member, a second B deflection member, and a second C deflection member, a part of the light emitted from the image formation device is incident on the first A deflection member, a light incident on the first A deflection member is deflected by the first A deflection member, totally reflected inside the first light guide plate and incident on the first B deflection member, deflected by the first B deflection member, totally reflected inside the first light guide plate and incident on the first C deflection member, deflected by the first C deflection member, and emitted toward a pupil of an observer, at least a rest of the light emitted from the image formation device is incident on the second A deflection member, a light incident on the second A deflection member is deflected by the second A deflection member, totally reflected inside the second light guide plate, incident on the second B deflection member, deflected by the second B deflection member, totally reflected inside the second light guide plate, incident on the second C deflection member, deflected by the second C deflection member, and emitted toward the pupil of the observer, and when a direction in which a propagation direction of a light deflected by the first B deflection member in the first light guide plate is orthogonally projected onto the first light guide plate is a first direction, and a direction in which a propagation direction of a light deflected by the second B deflection member in the second light guide plate is orthogonally projected onto the first light guide plate is a second direction, the first direction is opposite to the second direction.