A molecular detection chip including a metal oxide silicon-field effect transistor (MOSFET) on sidewalls of a micro-fluid channel and a molecular detection device including the molecular detection chip are provided. A molecular detection method, particularly, qualification methods for the immobilization of molecular probes and the binding of a target sample to the molecular probes, using the molecular detection device, and a nucleic acid mutation assay device and method are also provided. The formation of the MOSFET on the sidewalls of the micro-fluid channel makes easier to highly integrate a molecular detection chip. In addition, immobilization of probes directly on the surface of a gate electrode ensures the molecular detection chip to check for the immobilization of probes and coupling of a target molecule to the probes in situ.