Provided is a method and a system for detecting an error focus calibration, wherein a first DFOV value is measured in a state before the collimator lens is interposed between the resolution chart and the camera module, and a second DFOV value is measured in a state after the collimator lens is interposed between the resolution chart and the camera module, a determination is made whether a value obtained by subtracting the second DFOV value from the first DFOV value is smaller than a threshold value, and detecting as an error of auto calibration, in a case the subtracted value is greater than the threshold value.