PROBLEM TO BE SOLVED: To provide a chair capable of highly accurately detecting a physical signal from a seated person.SOLUTION: A chair with a leg includes a cushion pan F21, a back pan F22, and an awakening apparatus. The awakening apparatus includes: a respiration sensor 9 arranged in the cushion pan F21 or the back pan F22 so as to detect the physical signal of a seated person; a vibration device for stimulating the seated person; and a control device for controlling the vibration device. At least one of the cushion pan F21 and the back pan F22 includes a pad F21o. The respiration sensor 9 is arranged in the thickest portion of the pad F21o arranged in the cushion pan F21 or the back pan F22.SELECTED DRAWING: Figure 3