PURPOSE: To manufacture at favorable productivity a ligneous board superior in water resistance and durability, by a method wherein in the case where a ligneous board is manufactured by a steam injection method, a resin composition in which mol ratios each of melamine, phenol and formaldehyde are specified respectively is used as a binder.

CONSTITUTION: A ligneous board is manufactured by a steam injection method. In this case, a specific resin composition is used as a binder. Then in the specific resin composition, mol ratios of melamin and phenol are established within a range of phenol (P)/melamine(M)=0.3 to 1.0. Then the mol ratio F/M of formaldehyde (F) and melamine is established so as to satisfy the following formulas each as a function of P/M. They are F/M≥3X(P/M)+3/2 and F/M≤4X (P/M)+3. Furthermore, a methylene bond is not allowed to exist between the phenol and melamine. With this construction, the ligneous board superior in water resistance and durability is manufactured at favorable productivity industrially.