A sample observation device comprising: an emission optical system configured to emit planar light onto a sample; a scanning unit configured to scan the sample with respect to an emission face of the planar light at a constant speed; an imaging optical system having an observation axis inclined with respect to the emission face and configured to form an image from observation light generated in the sample in accordance with the emission of the planar light; an image acquiring unit configured to acquire a plurality of partial image data corresponding to a part of an optical image according to the observation light formed as an image by the imaging optical system; and an image generating unit configured to generate observation image data of the sample based on the plurality of partial image data generated by the image acquiring unit; wherein the image acquiring unit is further configured to acquire the plurality of partial image data during scanning of the sample by the scanning unit; wherein the partial image data is read from only a sub array of pixel columns in a light receiving surface of an area image sensor, wherein the sample is held by a sample container having an input face of the planar light, and an optical axis of the planar light according to the emission optical system is orthogonal to the input face of the sample container, wherein the scanning unit is further configured to scan the sample in a direction orthogonal to the optical axis of the planar light according to the emission optical system; and wherein the image generating unit is further configured to generate observation image data of the sample on a face orthogonal to the optical axis of the planar light based on the plurality of partial image data. an emission optical system configured to emit planar light onto a sample; a scanning unit configured to scan the sample with respect to an emission face of the planar light at a constant speed; an imaging optical system having an observation axis inclined with respect to the emission face and configured to form an image from observation light generated in the sample in accordance with the emission of the planar light; an image acquiring unit configured to acquire a plurality of partial image data corresponding to a part of an optical image according to the observation light formed as an image by the imaging optical system; and an image generating unit configured to generate observation image data of the sample based on the plurality of partial image data generated by the image acquiring unit; wherein the image acquiring unit is further configured to acquire the plurality of partial image data during scanning of the sample by the scanning unit; wherein the partial image data is read from only a sub array of pixel columns in a light receiving surface of an area image sensor, wherein the sample is held by a sample container having an input face of the planar light, and an optical axis of the planar light according to the emission optical system is orthogonal to the input face of the sample container, wherein the scanning unit is further configured to scan the sample in a direction orthogonal to the optical axis of the planar light according to the emission optical system; and wherein the image generating unit is further configured to generate observation image data of the sample on a face orthogonal to the optical axis of the planar light based on the plurality of partial image data.