A cowl structure including a cowl box having a partition panel joined to both rear and bottom walls thereof inside the cowl box. The partition panel constitutes, together with the rear and bottom walls, a hollow member portion extending in a vehicle width direction. An outside air introducing port is provided in the cowl box, for introducing outside air into the cowl box outside of the member portion. A communication port is provided in the partition panel, for allowing the inside and outside of the member portion to communicate with each other inside the cowl box. An air supplying port is provided in the rear wall at a location spaced upward from the bottom wall, for allowing the inside of the member portion and a vehicle compartment to communicate with each other. The communication port and the air supplying port overlap each other in the vehicle width direction.