An image pickup device, comprising: an observation target holding unit that holds an observation target; a detection unit in which detection elements for detecting light emitted from the observation target are arranged in a two-dimensional manner; a lens unit which is disposed between the observation target holding unit and the detection unit and in which a plurality of lens arrays, each of which includes a plurality of refractive index distribution type lenses that are linearly arranged, are arranged in a direction perpendicular to an arrangement direction of the refractive index distribution type lenses and a lens holding unit between the lens arrays; characterized in further comprising: a moving mechanism configured to move the lens unit or the observation target holding unit and the detection unit in the perpendicular direction; and a moving mechanism control unit configured to control the moving mechanism, wherein the moving mechanism control unit is configured to control the moving mechanism such that the lens unit or the observation target holding unit and the detection unit are moved to a second position from a first position, and an image forming unit that forms an image by superposing a first image detected at the first position by the detection unit and a second image detected at the second position by the detection unit; wherein the lens holding unit blocks the light between the lens arrays; and the second position is a position at which the lens arrays of the lens unit after the movement are disposed at respective positions facing a detection surface of the detection unit that are shielded by the lens holding unit when the lens unit is disposed at the first position. an observation target holding unit that holds an observation target; a detection unit in which detection elements for detecting light emitted from the observation target are arranged in a two-dimensional manner; a lens unit which is disposed between the observation target holding unit and the detection unit and in which a plurality of lens arrays, each of which includes a plurality of refractive index distribution type lenses that are linearly arranged, are arranged in a direction perpendicular to an arrangement direction of the refractive index distribution type lenses and a lens holding unit between the lens arrays; characterized in further comprising: a moving mechanism configured to move the lens unit or the observation target holding unit and the detection unit in the perpendicular direction; and a moving mechanism control unit configured to control the moving mechanism, wherein the moving mechanism control unit is configured to control the moving mechanism such that the lens unit or the observation target holding unit and the detection unit are moved to a second position from a first position, and an image forming unit that forms an image by superposing a first image detected at the first position by the detection unit and a second image detected at the second position by the detection unit; wherein the lens holding unit blocks the light between the lens arrays; and the second position is a position at which the lens arrays of the lens unit after the movement are disposed at respective positions facing a detection surface of the detection unit that are shielded by the lens holding unit when the lens unit is disposed at the first position. a moving mechanism configured to move the lens unit or the observation target holding unit and the detection unit in the perpendicular direction; and a moving mechanism control unit configured to control the moving mechanism, wherein the moving mechanism control unit is configured to control the moving mechanism such that the lens unit or the observation target holding unit and the detection unit are moved to a second position from a first position, and an image forming unit that forms an image by superposing a first image detected at the first position by the detection unit and a second image detected at the second position by the detection unit; wherein the lens holding unit blocks the light between the lens arrays; and the second position is a position at which the lens arrays of the lens unit after the movement are disposed at respective positions facing a detection surface of the detection unit that are shielded by the lens holding unit when the lens unit is disposed at the first position.