A LED-based lamp apparatus includes a LED unit having multiple LEDs connected in series, a step-up circuit for stepping up a power supply voltage by a switching action of a switching element to supply an electric current to the LED unit, a sensing element for measuring a value of the current, and a controlling element connected in series with the LED unit to control the current based on the measured current value. When some of the LEDs of the LED unit are broken and short-circuited due to, for example, long-term use, the current increases instantaneously and an overcurrent condition occurs. In this case, the controlling element limits the current immediately to correct the overcurrent condition. Thus, the controlling element prevents the overcurrent condition from causing a secondary failure to normal LEDs of the LED unit.