The invention discloses a V-belt slitting and chamfering device and a V-belt machining method, and belongs to the technical field of V-belt production. The V-belt slitting and chamfering device comprises a V-belt forming roller, a cylinder blank slitting mechanism and a V-belt chamfering mechanism, wherein the V-belt forming roller is arranged at the upper end of a forming roller bracket; the cylinder blank slitting mechanism comprises a tool support, a cylinder blank slitting tool and a first tool feeding component; the first tool feeding component is arranged at the top of the tool support;the cylinder blank slitting tool is arranged on the first tool feeding component; the V-belt chamfering mechanism comprises a chamfering tool base, a chamfering tool assembly and a third tool feedingcomponent; the third tool feeding component is arranged in the middle of the tool support; the chamfering tool base is arranged on the third tool feeding component; and the chamfering tool assembly isarranged at the front end of the chamfering tool base. Compared with a traditional V-belt production mode, slitting and chamfering cutting processes can be performed simultaneously according to the V-belt slitting and chamfering device and the V-belt machining method, and discharging, transferring and feeding processes from the slitting process to the chamfering process are omitted, so that production efficiency is greatly improved; and the produced V-belt finished product is high in quality and good in consistency.