A damper apparatus for an input shaft of a transmission, may include a flywheel having a reception space in which a inertial body may be provided so as to be rotatable relative to the flywheel, the input shaft extending into the reception space of the flywheel, and an inertial body assembly slidably coupled to the input shaft so as to provide rotational inertial force to the input shaft, the inertial body assembly being disposed in the reception space.