The invention discloses a machining method for a spherical involute toothed oblique straight bevel gear made by taped teeth. The machining method for a bevel gear adopts methods of gear skiving, gear milling and gear grinding. The methods of gear skiving, gear milling and gear grinding have the common technical characteristics that an oblique straight line ML on the big circular plane (Q) of a spherical surface, which is tangent to a toothed portion tangent circle with the radius of R0, represents a skiving cutter edge on an imaginary gear or uses a tangent plane which contains the ML and is perpendicular to the big circular plane (Q) of a spherical surface as the rotating plane of a single angle milling cutter end edge or the end surface of a grinding wheel, so a gear blank base cone with the base cone angle Delta b is tangent to the big circular plane (Q) of a spherical surface and the relative pure rolling is completed, the involute surface tooth cutting of the base cone is carriedout to obtain the oblique straight bevel gear flank with the spherical involute teeth. In order to avoiding overcutting, the ML line for representing a skiving gear cutter edge or a straight line along the gear root cuts out along a straight line of the gear root with the cutting-out speed or along the ML self straight line with the speed of a cutting-out speed. One side flank of a gear is cut according to single tooth division. The machining of two side flanks is completed by adopting double cutter heads and double stations to cut teeth. A new machine tool is designed according to the method.