The present invention provides metal surface treatment agents and metal surface treatment methods which can form a high anticorrosion coating without use of hexavalent chromium compounds which are a cause of environmental pollution. In the present invention, a metal surface is coated with a metal surface treatment agent made of a composition containing a compound containing at least one or more mercapto groups per molecule and, depending upon need, a curing agent, curing catalyst and/or silica and the coating of the metal surface treatment agent is heat-treated.