A device for mobile object, which is usable in a mobile object, includes an occupant information specifying unit and a request estimation unit. The occupant information specifying unit specifies an occupant information record for each of multiple occupants existing in the mobile object by distinguishing the multiple occupants from one another. The multiple occupants are detected by a sensor of the mobile object. The request estimation unit estimates a request of one of the multiple occupants corresponding to a combination of the occupant information records of the multiple occupants based on the occupant information records of the multiple occupants specified by the occupant information specifying unit.