To provide a formaldehyde trapping agent which suppresses the diffusion of formaldehyde caused by a formaldehyde type adhesive used at the time of production of a woody material over a long period of time, and prevents the discoloration of the woody material and the corrosion of the metal member of woody material manufacturing equipment.

The formaldehyde trapping agent contains 1-15 pts.wt. of a sulfite, 0.1-4 pts.wt. of boric acid and 0.05-2 pts.wt. of a rustproof agent as main components and is used as an aqueous solution.