An interpolation method based on edge detection includes: generating a measurement value of an edge direction according to a first pixel set and a second pixel set, wherein the first pixel set comprises at least a first pixel, the second pixel set comprises at least a second pixel, the first pixel and the second pixel are on opposite sides of the target location and define the edge direction, and the measurement value represents a measure of variance between the first pixel set and the second pixel set; according to the above step, generating a plurality of measurement values corresponding to a plurality of edge directions respectively; identifying a minimum measurement value from the plurality of measurement values; and calculating a value of the target pixel according to pixels of the first and second pixel sets corresponding to the minimum measurement value.