Image processing is a highly useful method for measuring corrosion of steel and cracks in concrete. However, binary image processing method of the existing studies had the disadvantage of low accuracy and being represented only in black and white. To solve this issue, crack evaluation of specimens between the red and blue spectrum was performed using image processing. The crack of the specimen caused by the freeze-thaw test was represented in blue using image processing, and the crack area was evaluated in terms of the ratio to the overall area.