An heat treatment apparatus for a vehicle body component includes, a jig base, a lower fixed die fixedly installed on the jig base and supporting the vehicle body component that is press-molded into a predetermined shape, a heating unit installed on the lower fixed die and locally heating the vehicle body component, a plurality of side movable dies that can move reciprocally disposed at both sides of the lower fixed die, installed on the jig base, and selectively combinable with the lower fixed die, a cooling unit installed on each side movable die and cooling a heating portion of the vehicle body component, and an upper movable die that can move reciprocally in the up and down direction correspondingly to the lower fixed die, and configured to clamp the vehicle body component through the lower fixed die and at least one of the side movable dies combined together.