A human face detection device includes a photosensitive element, a human face detection unit, and a skin color threshold generation unit. The photosensitive element is used for capturing a first image containing a first human face block. The human face detection unit compares the first image with at least one human face feature, so as to detect the first human face block. The skin color threshold generation unit is used for updating a skin color threshold value according to the detected first human face block. The skin color threshold value is used for filtering the first image signal to obtain a candidate region, the human face detection unit compares the candidate region with the at least one human face feature to obtain the first human face block, and the skin color threshold value determines whether the first human face block detected by the human face detection unit is correct.