An object detecting device, an object detecting method and a non-transitory computer-readable medium are provided. The object detecting method includes the following steps: A classifier generates a current color image and a current gray scale image. The classifier generates an initial characteristic pattern from the current color image via a neural network algorithm. The classifier adjusts a current dimension of the initial characteristic pattern to generate an adjusted characteristic pattern according to a gray scale image dimension of the current gray scale image. The classifier concatenates the adjusted characteristic pattern and the current gray scale image to calculate a class confidence. The classifier determines whether the class confidence is larger than a confidence threshold, and outputs a current classification result if the class confidence is larger than the confidence threshold. A storage device stories the current classification result.