A culture observation apparatus, which is used for observing a cultured cell while culturing the cell, includes a culture device that forms a culture space which is controlled to be an environment suitable for culturing the cultured cell; a sample tray that holds a container housing the cultured cell and a culture medium; a microscope that serves for observing the cultured cell; a tray holding mechanism that holds the sample tray in the culture space in a detachable manner with good reproducibility; and a shifting mechanism that relatively shifts the sample tray held by the tray holding mechanism and a light axis of the microscope along a plane that is orthogonal to the light axis, wherein the sample tray has a heater used for heating the sample tray, and is electrically connectable to an energy supplying unit that supplies energy to the sample tray.