A work piece feeding and conveying device for a planing machine includes a foundation base, an intermediate base and an upper base. The intermediate base is assembled with a convey unit and the upper base is pivotally provided with a plane knife. A motor is installed between the convey unit and the foundation base, having its driving shaft fixed thereon with a first driving wheel and a second driving wheel. A first transmission member and a second transmission member respectively pass around the first and the second driving wheel. The first transmission member has another end passing around a knife shaft, while the second transmission member has another end going around the convey unit. Thus, the plane knife and the convey unit can respectively be driven to rotate by the first and the second transmission member separately disposed on the driving shaft of the same motor.