To provide a bathroom ventilation system capable of providing a comfortable bath time without generating cold draft in taking a bath.

In a bathroom composed of a bathing room 1, a dressing room 2 and a bathing room inlet door 3 partitioning the bathing room 1 and the dressing room 2, ventilating holes are respectively formed on both of the bathing room 1 and the dressing room 2, a duct 12 connected with the ventilating hole 11 of the bathing room and a duct 22 connected with the ventilating hole 21 of the dressing room are connected with an exhaust system 7 through a switch valve 6, and the switch valve is switched to connect the dressing room ventilating duct 22 and the exhaust system 7 when the presence of a person taking a bath in the bathing room is judged by a ventilation control means 5, and switched to connect the bathing room ventilating duct 12 and the exhaust system 7 in the case excluding the case to perform the exhaust ventilation.