The present invention relates to a target gene-detecting device and a method for detecting a target gene. According to an aspect, a target gene-detecting device can be conveniently fabricated at low cost by employing a porous substrate or a method for detecting a target gene allows the pretreatment of a sample, the extraction of a nucleic acid, the amplification of a nucleic acid, and the detection of a target gene to be conducted at high accuracy and specificity in an integral system, with no contamination plausibility and can be thus useful for gene inspection.