A stress alleviation system, includes: a biological sensor measuring first biological data of a customer boarding transportation； an action application apparatus provided to a transportation seat and applying an action to the customer for alleviating a stressed state of the customer sitting on the seat； a stress data saver previously saving specific stress data where a customer identifier identifying the customer and a second stress indicator calculated using second biological data measured in past boarding of the customer are associated； a stressed state assessor assessing whether the customer is in the stressed state by calculating a first stress indicator of the customer on board using the first biological data of the customer, and by comparing the first stress indicator with the second stress indicator； and an action controller transmitting a control signal causing the action to the action application apparatus when the customer is assessed as in the stressed state.
