An operational data storage device mounted on an hydraulic excavator is programmed to store operational data including stroke data and movement quantity data. The stroke data represent input operations by the operator of the hydraulic excavator through electric operating levers, and the movement quantity data represent movement quantities of operating members for a front working device equipped with the hydraulic excavator, the operating member being operated according to the input operations. The operational data storage device stores, in an initial state, the operational data in the volatile storage section, generates a save and exit signal if a posture parameter detected at a posture detection sensor included in the hydraulic excavator exceeds a predetermined posture threshold, and responsive to the save and exit signal, switches a write destination of the operational data from the volatile storage section to the non-volatile storage section.