A multimonitor (display unit) is mounted in a mobile construction machine including an undercarriage and working equipment each driven by an engine, the multimonitor receiving a data of instant fuel consumption from a controller for controlling a fuel quantity to be supplied to the engine. The multimonitor includes a display including a single eco gauge (fuel-consumption indicator) for displaying fuel consumption in a street mode in which an undercarriage is operated and fuel consumption in a work mode in which working equipment is operated, a 100%-gauge fuel-consumption calculator that calculates a full-scale fuel consumption value in a full scale of the eco gauge based on target fuel consumption in the respective modes, and a gauge-display-value calculator that calculates a ratio of the instant fuel consumption to the 100% fuel consumption calculated by the 100%-gauge fuel-consumption value calculator.