In order to prevent, in a resin sealing step, a conductive foil 10 from locally rising because of concentration of air intervening between the conductive foil 10 and lower mold 28A due to the charged pressure, a method for manufacturing circuit devices is provided. The method for manufacturing circuit devices includes the step of forming conductive patterns 21, which form a plurality of mounting portions 15 of a circuit element 22 on a conductive foil 10, in each block 12, the step of disposing the circuit element 22 on each mounting portion 15 of the conductive pattern 21 in each block 12, the step of performing resin sealing by bringing the lower mold 28A having an air vent 30 into contact with the backface of the conductive foil 10 in each block 12 and by performing transfer molding with an insulating resin 20 while disposing each mounting portion 15 of the block 12 in the same cavity, and the step of separating each mounting portion 15 by dicing.