It is intended to provide a sound insulation structure for a vehicle, which is capable of adequately retaining an elongated line component, such as a wiring harness, a pipe or a cable, while suppressing deterioration in sound insulation performance by a sound insulator. In the sound insulation structure, a sound insulator is provided in a void space surrounded by: a front fender panel; a cowl side member disposed on a vehicle inward side with respect to the front fender panel to extend in a vehicle front-rear direction; and a mud guard disposed just below the front fender panel and the cowl side member to form a wheel housing. The sound insulator is formed using an elastically-deformable urethane foam. The sound insulator is formed with a slit capable of clamping a regenerative brake wiring harness laid to extend in the vehicle front-rear direction and pass through the void space.