The present invention relates to a biosensor specifically detecting a protein kinase A (PKA), and a diagnosis kit comprising the biosensor. In particular, the present invention relates to a biosensor for detecting a PKA comprising a cantilever, and a protein kinase inhibitor (PKI) immobilized on the surface of the cantilever; and a kit for diagnosing diseases caused by the increase of the activity of a protein kinase, comprising a sample, the biosensor, and a quantification manner.