A circuit substrate processing laminate has, sequentially in the order of a support, a temporary adhesive material layer releasably laminated on the support, and a circuit substrate. The circuit substrate has a front surface on which a circuit is formed and a back surface to be processed. The temporary adhesive material layer is releasably laminated to the front surface, and is composed of a thermosetting siloxane polymer layer laminated on the support, after cured, has a first peeling force of 10 to 500 mN/25 mm as measured by a 180° peel test. The first peeling force is required for peeling the polymer layer from an interface with the support. The polymer layer, after cured, has a second peeling force of 50 to 1000 mN/25 mm as measured by the 180° peel test. The second peeling force is required for peeling the polymer layer from an interface with the circuit substrate.