A desired property is readily granted to a wooden piece (1) subjected to compression. When the wooden piece (1) is processed by a pair of metal molds (51, 61), a property granting liquid (101) is applied to a surface of at least one (61) of the metal molds (51, 61) which comes into contact with a surface of the wooden piece (1). The property granting liquid (101) is in liquid state at temperatures of 5 to 35 C and grants a certain property to the surface of the wooden piece (1). The wooden piece (1) is sandwiched and compressed by the pair of metal molds (51, 61) including the metal mold (61) to which the property granting liquid (101) is applied.