PROBLEM TO BE SOLVED: To provide a virtual image observation device that offers desired functions without requiring an increase in size and preparation of multiple types of ocular optical units, and to provide inner optical systems for the same.SOLUTION: A virtual image observation device 100 of the present invention comprises a display element 108, an ocular optical unit 131, a housing 114, 132 that holds the display element and ocular optical unit, and a mounting section 132a for interchangeably mounting an inner optical system 140 in an image light path between the display element and ocular optical unit in the housing.【課題】装置の大型化や多種類の接眼光学部の準備を要することなく、所望の機能が得られる虚像観察装置及び虚像観察装置のインナー光学系を提供する。【解決手段】本発明の虚像観察装置１００は、表示素子１０８と、接眼光学部１３１と、表示素子及び接眼光学部を保持する筐体１１４、１３２と、表示素子と接眼光学部との間の画像光の光路内で、筐体にインナー光学系１４０を交換可能に装着するための装着部１３２ａと、を備えている。【選択図】図４
