A wearable device comprises a band structure, a main body, a micro air pump, an airbag, a driving control module, a sensor and an optical sensor. The micro pump is disposed within the receiving space. The sensor is disposed on the driving control module and connected with the micro air pump. The driving control module control the micro air pump to operate, making gas transported from the micro air pump to the airbag so that the airbag is inflated and expended to be fixed on a specific part of the user. The user is able to select the sensor to detect the physiological data, by which a precise detection is achieved. The user is also able to select the optical sensor to detect the physiological data, by which a rapid detection is achieved, and the physiological data is sent to the driving control module to be recorded.
