Disclosed herein is a mobile x-ray imaging apparatus having an improved structure to reinforce security of an x-ray detector. A mobile x-ray imaging apparatus includes an x-ray source configured to generate and radiate x-rays, one or more x-ray detectors provided to detect the x-rays radiated from the x-ray source, a storage unit having one or more slots in which the one or more x-ray detectors are stored, and one or more locking units installed in the storage unit to limit withdrawal of the one or more x-ray detectors stored in the one or more slots, wherein the one or more locking units may include a pressing member provided to be pressable and one or more rotating members configured to directly receive a pressing force of the pressing member and provided to rotate and protrude toward an inside of the one or more slots.