A microinjection apparatus, which injects an object into a cell with a needle, acquires a first image that is an image of the cell at a first focal position and a second image that is an image of the cell at a second focal position, and decides a state of the cell based on a difference image obtained from the first image and the second image. Execution of such sequence of processing makes it possible to measure a state of a cell without involving human work and confirm the state of the cell in performing a microinjection, without a necessity of experienced skill, efficiently, and simply.