A microinjection apparatus of the present invention includes a needle-position polarity detecting unit that detects a position of the needle in the vertical direction at which a value of a differential aggregate distribution becomes the maximum in the situation in which a shape of the leading edge of the needle at a focal position narrows at the right. Moreover, a differential-average determining unit, based on a differential average of an image near the position detected by the needle-position polarity detecting unit, determines the lowest allowable position of the needle, which is a position at which a differential average exceeds a predetermined threshold.