Provided are a mobile X-ray apparatus and a method of operating the same. The mobile X-ray apparatus may include an X-ray emitter； a battery configured to supply operating power to the X-ray emitter； and a controller configured to calculate an internal resistance value of a battery based on an overcurrent generated when X-rays are emitted by an X-ray emitter, and determine a degradation state of the battery by using the calculated internal resistance value.
