1. An image measurement apparatus, comprising: a issue region recognition unit configured to recognize a tissue region from an image which is imaged by staining tissue including a measurement object and a non-measurement object; a partial image extraction unit configured to extract images of an predetermined size and a fixed magnification from the tissue region; a mask generation unit configured to generate a mask to remove a non-measurement object region, which is a region in which the non-measurement object exists, from the tissue region for each of the extracted images; a whole mask generation unit configured to generate a provisional whole mask by merging masks generated for each of the images and generate a whole mask by merging portions which are not masked in the provisional whole mask, the portions adjacent to each other into one or more object regions; a measurement unit configured to measure, for each of the images extracted by the partial image extraction unit, information on the measurement object contained in the images; and a region information computation unit configured to compute, based on the measured information and the whole mask, information on the measurement object for each of the object regions.