A chair device, a mattress device, and a propping device are provided. The chair device includes a support stand, a seat module disposed above the support stand, a connection module disposed at one side of the seat module, a back support module connected to the connection module and disposed at one side of the seat module, a first pressure adjustment module disposed in the seat module, a second pressure adjustment module disposed in the back support module, a first pressure sensing module disposed in the seat module, a second pressure sensing module disposed in the back support module, and a control module. The control module adjusts the first pressure adjustment module according to first sensed pressure signals from the first pressure sensing module, and adjusts the second pressure adjustment module according to second sensed pressure signals from the second pressure sensing module.