1. A biological image acquisition device comprising: a specimen support for supporting a biological specimen placed thereon; a two-dimensional detector; an image pickup optical system for leading, to the two-dimensional detector, light traveling in a direction toward the two-dimensional detector from the specimen placed on the specimen support and light traveling in another direction from the specimen, and for forming images of these lights on the two-dimensional detector; a light source system comprising a light source arranged outside a field of view of the two-dimensional detector for irradiating the specimen placed on the specimen support with light, the field of view being formed by the image pickup optical system; and an image display device for displaying images picked up by the two-dimensional detector.