According to one embodiment, an illumination device includes a first member, a second member, a first light source. The first member includes a first prism array including first prisms aligned in a first direction. The second member includes a second prism array including second prisms aligned in a second direction. The second member disposed more closely to a first A side than to the first member. The first light source disposed more closely to a second A side than to the second member to apply a parallel light beam to a second B side. The parallel light beam from the first light source is made incident on the second prism array and incident on the first prism array without passing through a light guide.