To provide an energy regenerating device for a vehicle, and a catalyst postprocessing system after heating capable of preventing heat damage.

This energy regenerating device has a control device 37 for controlling operation of an energy recovering means for recovering kinetic energy of the vehicle 10, and an operation state detecting means for detecting an operation state of the vehicle 10; and operates the energy recovering means by the control device 37 when determining that the operation state of the vehicle 10 is in an energy recovering area on the basis of a detecting result by this operation state detecting means; and has an intake control valve 36 openable-closable in response to the opening-closing timing of an intake valve 26 in an intake passage 29; and also has an opening-closing timing setting part for setting the opening-closing timing of the intake control valve 36 so as to minimize negative work of an engine 10; and controls opening-closing of the intake control valve 36 so as to become this set opening-closing timing.