A method of measuring feeding velocity of a web, on which a scale having pitches different from pitches of a mask are formed, is provided. The method includes: calculating a number of vibrations of a moiré image of light passing through the mask and the scale; calculating pitches of the scale of the fed web based on the calculated number of vibrations of the moiré image; averaging the pitches of the scale so that a change in a pitch between adjacent timings among the calculated pitches of the scale is minimized; extracting first signals corresponding to our phases for one pitch based on the averaged pitches of the scale; calculating two second signals for forming a Lissajous circle from the first signals; and calculating an angle of the Lissajous circle by the two second signals and then calculating the feeding velocity of the web by using the calculated angle.