An image acquisition apparatus comprising:; a chassis and a connecting part for detachably connecting the chassis to a microscope; an opening in the connecting part that allows light from a specimen collected by the microscope to enter the image acquisition apparatus along an entrance optical axis; a light-path setting member configured to make the incident light enter at least a first light path and a second light path; and at least a first imaging device and a second imaging device, the first imaging device being a color CCD having an optical axis perpendicular to its imaging surface and being aligned with the entrance optical axis and the second imaging device being a monochrome CCD having an optical axis perpendicular to its imaging surface and being located parallel to the optical axis (11 a) of the color CCD with a gap interposed there between, the first imaging device arranged to acquire images of light entering the first light path set by the light-path setting member and the second imaging device arranged to acquire images of light entering the second light path set by the light-path setting member; wherein the light-path setting member includes a prism having parallelepiped shape having two reflecting surfaces disposed in parallel with a gap interposed between or two mirrors parallel to each other and a swivel mechanism configured to support the prism or the mirrors in a manner allowing it to swivel about a swivel axis that is parallel to the optical axes (11a, 12a) of the first imaging device and the second imaging device and move the prism or the mirrors between a position on the entrance optical axis and a position shifted from the entrance optical axis, such that a light beam entering the chassis via the opening is directly imaged by the color CCD, when the prism or mirror is removed from the light path between the opening and the color CCD without passing through the light path setting member and a light beam entering the chassis via the opening is reflected by the two reflecting surfaces of the prism or the mirrors and is then imaged by the monochrome CCD, when the light path setting member is inserted in the light path between the opening and the color CCD, and the image acquisition apparatus further comprises a moving means to which at least the first imaging device is attached and that is configured to move the first imaging device in a direction perpendicular to the optical axis of the first imaging device by half the pixel pitch of the color CCD to configure a pseudo color CCD in which a large number of pixels is arrayed with a short pixel pitch, thus acquiring a high-resolution image. a chassis and a connecting part for detachably connecting the chassis to a microscope; an opening in the connecting part that allows light from a specimen collected by the microscope to enter the image acquisition apparatus along an entrance optical axis; a light-path setting member configured to make the incident light enter at least a first light path and a second light path; and at least a first imaging device and a second imaging device, the first imaging device being a color CCD having an optical axis perpendicular to its imaging surface and being aligned with the entrance optical axis and the second imaging device being a monochrome CCD having an optical axis perpendicular to its imaging surface and being located parallel to the optical axis (11 a) of the color CCD with a gap interposed there between, the first imaging device arranged to acquire images of light entering the first light path set by the light-path setting member and the second imaging device arranged to acquire images of light entering the second light path set by the light-path setting member; wherein the light-path setting member includes a prism having parallelepiped shape having two reflecting surfaces disposed in parallel with a gap interposed between or two mirrors parallel to each other and a swivel mechanism configured to support the prism or the mirrors in a manner allowing it to swivel about a swivel axis that is parallel to the optical axes (11a, 12a) of the first imaging device and the second imaging device and move the prism or the mirrors between a position on the entrance optical axis and a position shifted from the entrance optical axis, such that a light beam entering the chassis via the opening is directly imaged by the color CCD, when the prism or mirror is removed from the light path between the opening and the color CCD without passing through the light path setting member and a light beam entering the chassis via the opening is reflected by the two reflecting surfaces of the prism or the mirrors and is then imaged by the monochrome CCD, when the light path setting member is inserted in the light path between the opening and the color CCD, and the image acquisition apparatus further comprises a moving means to which at least the first imaging device is attached and that is configured to move the first imaging device in a direction perpendicular to the optical axis of the first imaging device by half the pixel pitch of the color CCD to configure a pseudo color CCD in which a large number of pixels is arrayed with a short pixel pitch, thus acquiring a high-resolution image.