A cell observation device comprising: a reflection interference measurement light source; reflection interference light quantity adjustment means which is adapted to adjust a light quantity of light emitted from the reflection interference measurement light source; a quantitative phase measurement light source; quantitative phase light quantity adjustment means which is adapted to adjust a light quantity of light emitted from the quantitative phase measurement light source; imaging means which is adapted to image reflected light from a cell, of the light emitted from the reflection interference measurement light source, to generate a reflection interference image, and which images transmitted light through the cell, of the light emitted from the quantitative phase measurement light source, to generate a quantitative phase image; first extraction means which is adapted to extract a first parameter from the reflection interference image generated by the imaging means; and second extraction means which is adapted to extract a second parameter from the quantitative phase image generated by the imaging means, wherein during generation of the reflection interference image, the quantitative phase light quantity adjustment means blocks the light from the quantitative phase measurement light source and the imaging means images the reflected light, and wherein during generation of the quantitative phase image, the reflection interference light quantity adjustment means is adapted to block the light from the reflection interference measurement light source and the imaging means is adapted to image the transmitted light; the cell observation device further comprising: an interference optical system which is adapted to separate the transmitted light into object light and reference light and is adapted to cause interference between the object light and the reference light to generate the quantitative phase image; and reference light blocking means which is adapted to block the reference light during the generation of the reflection interference image; and an objective lens which is adapted to condense the light emitted from the reflection interference measurement light source and reflected from the cell; and a slit of a ring shape at a position conjugate with an aperture stop on the reflection interference measurement light source side of the objective lens. a reflection interference measurement light source; reflection interference light quantity adjustment means which is adapted to adjust a light quantity of light emitted from the reflection interference measurement light source; a quantitative phase measurement light source; quantitative phase light quantity adjustment means which is adapted to adjust a light quantity of light emitted from the quantitative phase measurement light source; imaging means which is adapted to image reflected light from a cell, of the light emitted from the reflection interference measurement light source, to generate a reflection interference image, and which images transmitted light through the cell, of the light emitted from the quantitative phase measurement light source, to generate a quantitative phase image; first extraction means which is adapted to extract a first parameter from the reflection interference image generated by the imaging means; and second extraction means which is adapted to extract a second parameter from the quantitative phase image generated by the imaging means, an interference optical system which is adapted to separate the transmitted light into object light and reference light and is adapted to cause interference between the object light and the reference light to generate the quantitative phase image; and reference light blocking means which is adapted to block the reference light during the generation of the reflection interference image; and an objective lens which is adapted to condense the light emitted from the reflection interference measurement light source and reflected from the cell; and a slit of a ring shape at a position conjugate with an aperture stop on the reflection interference measurement light source side of the objective lens.