The present invention relates to a metagenome-derived alkaline phosphatase, and more particularly to a novel, metagenome-derived alkaline phosphatase screened using a artificial genetic circuit that detects phenolic compounds, and a preparation method thereof. A novel alkaline phosphatase according to the present invention has high activity of dephosphorylating DNA and can be inactivated rapidly by simple heat treatment. Thus, it can be used for a dephosphorylation reaction so that genetic manipulations, including genetic cloning, become efficient. In addition, it can be actively expressed in recombinant microorganisms, and thus can be used in various assays, including enzyme immunoassay.