Abstract: A stress relieving device for vehicles includes a supply unit that sprays cedrol into a vehicle cabin, a detection unit that detects an irritation level and a sleepiness level of a passenger in the vehicle cabin, and a controller that operates the supply unit based on the irritation level detected by the detection unit to cause the cedrol to be volatilized into the vehicle cabin and operates the supply unit to reduce a volatilization amount of the cedrol when the detection unit detects sleepiness. When cedrol is volatilized to suppress irritation in the passenger, a relaxation effect is exhibited, but when relaxation is exceed to promote sleepiness, the volatilization amount of cedrol is reduced to suppress sleepiness.