An endoscopic distance measurement method, which causes a single wavelength light source in an observation unit at a front end of a flexible tube of an endoscope to emit a predetermined wavelength light to an object to be measured via a diffraction grating so as to form a zero-order bright spot, a positive first-order bright spot and a negative first-order bright spot on the surface of the object through optical diffraction, and then capture an image from the object, and then calculate a distance magnification using a first arithmetic logic, and then to calculate the actual distance between two adjacent bright spots of the predetermined wavelength light being projected on the object using a second arithmetic logic and then to calculate the distance between the diffraction grating and the zero-order bright spot using a third arithmetic logic.
