Disclosed are a crack measuring method that may automatically measure crack growth in a surface of a structure rapidly and exactly without influencing the structure using image processing scheme, and an apparatus thereof. The crack measuring method includes: irradiating light to a surface of a structure; converting reflected light, wherein the irradiated light is reflected from the surface of a structure, into an image signal and capturing images of the surface of a structure corresponding to the image signal at predetermined scan intervals through a camera; performing continuously a line scan on the crack parts in the captured images at predetermined scan intervals; and inspecting crack growth in the surface of a structure by identifying pixels with relatively higher or lower light intensity in the scan lines.