Method of manufacturing semiconductor device

Disclosed is a technique in which an excessive resin can be stably cut and removed in a molding step. In a step for separating part of a runner leading to a resin-sealing body from the resin-sealing body, the runner is formed by a first runner and a second runner coupled to the first runner and the resin-sealing body. The runner is separated from a middle of the second runner by supporting, with a first supporting portion, the second runner from the side of the second surface of a lead frame, and by pushing down, with a break pin, the first runner in the direction from the side of the first surface of the lead frame toward the side of the second surface thereof, while the resin-sealing body is in a condition of floating in the air.