A covering film (100) includes a first covering layer (10), a first adhesive layer (20), and a thermal conductive layer (30) sandwiched between the first covering layer (10) and the first adhesive layer (20). A thermal conductivity of the thermal conductive layer (30) is K1, K1=3˜65 W/m.K. A thermal conductivity of the first covering layer (10) is K2, K2=0.02˜3.0 W/m.K. A thermal conductivity of the first adhesive layer (20) is K3, K3=0.02˜1.0 W/m.K. A circuit board and its manufacturing method are also provided.