A microscope , comprising: a sample placement part having a placement surface on which to place a sample and a bottom face opposite to the placement surface ; an observation lens for receiving fluorescence from the sample ; and an optical unit for generating sheet light traveling in a direction parallel to an observation plane of the observation lens , the sheet light entering the sample placement part from the bottom face and passing through the sample placement part to irradiate the sample , the fluorescence passing through the sample placement part toward the bottom face to be received by the observation lens the microscope further comprising a fluid holding device for holding fluid between the observation lens and the sample placement part , wherein the fluid holding device comprises: a connection section for connection to the observation lens ; an end face so designed as to face the bottom face ; a transmission window through which the sheet light enters the sample placement part ; and a fluid holding section for holding the fluid inside itself; and wherein in a state where the fluid holding device is connected to the observation lens , the end face is substantially parallel to the bottom face , the sheet light passes through the transmission window and then through the fluid holding section to irradiate the sample , and the fluorescence passes through the fluid holding section to be received by the observation lens . a sample placement part having a placement surface on which to place a sample and a bottom face opposite to the placement surface ; an observation lens for receiving fluorescence from the sample ; and an optical unit for generating sheet light traveling in a direction parallel to an observation plane of the observation lens , the sheet light entering the sample placement part from the bottom face and passing through the sample placement part to irradiate the sample , the fluorescence passing through the sample placement part toward the bottom face to be received by the observation lens the microscope further comprising a fluid holding device for holding fluid between the observation lens and the sample placement part , wherein the fluid holding device comprises: a connection section for connection to the observation lens ; an end face so designed as to face the bottom face ; a transmission window through which the sheet light enters the sample placement part ; and a fluid holding section for holding the fluid inside itself; and wherein in a state where the fluid holding device is connected to the observation lens , the end face is substantially parallel to the bottom face , the sheet light passes through the transmission window and then through the fluid holding section to irradiate the sample , and the fluorescence passes through the fluid holding section to be received by the observation lens . a connection section for connection to the observation lens ; an end face so designed as to face the bottom face ; a transmission window through which the sheet light enters the sample placement part ; and a fluid holding section for holding the fluid inside itself; and wherein in a state where the fluid holding device is connected to the observation lens , the end face is substantially parallel to the bottom face , the sheet light passes through the transmission window and then through the fluid holding section to irradiate the sample , and the fluorescence passes through the fluid holding section to be received by the observation lens . <EOS>