A projection type exposure apparatus and method comprising an exposure illumination light source, an exposure illumination system, a mask or reticle on which an original pattern to be projected on the exposed matter is drawn, an optical projection system, a stage for retaining the exposed matter and a mechanism for finely moving the stage along the exposure optical axis. The apparatus is provided with an exposure detection pattern area on the mask, detection illumination means for projecting on the exposure detection pattern area a light ray which is the same or almost the same in wavelength as exposure light having a desired directivity, exposure detection means for detecting the transmitted or reflected light diffracted by 1 degree after the light carrying the image formed on the exposed matter by the light passed through the above-noted optical projection system after projection by the detection illumination means onto the exposure pattern and then diffracted goes in reverse through the above-noted optical projection system and forms an image again on the exposure pattern on the above-noted mask and a control circuit for driving and controlling the above-noted fine movement mechanism by using the signal obtained by the exposure detection means.