To simplify the manufacture of the jamb of a door frame by omitting cutting of the surface part of a wood base that was carried out for formation of a rebate.

Two parallel vertical grooves 6 are formed in the surface part of a wooden base 1 and in positions matching the right and left end portions of a rebate 3. A cover member 2 inserted at one end into one of the vertical grooves and extending to the side end of the surface part of the wooden base closer from the vertical groove and to an end face is attached to the wooden base. The cover member has a thickness t equal to the depth d of the rebate. Two cover members are attached to the right and left ends of the wooden base and the rebate is formed in the surface part of the wooden base between the two cover members.