Disclosed is a lock-catch fitting structure of an electric air-purifying respirator of an auto-darkening welding mask. The electric air-purifying respirator comprises a housing (10) and a battery device. A battery holder is arranged on the housing (10), and by virtue of the lock-catch fitting structure, the battery device is detachably installed in the battery holder. The lock-catch fitting structure comprises at least four pairs of sliding engagement structures respectively formed on the battery device and on the battery holder, and a locking structure arranged in the battery device. Engagement or disengagement of each of the sliding engagement structure pairs can be formed by the sliding thereof relative to each other. The locking structure comprises a button (80) and a locking tongue (85) actuated by the button (80). The moving direction of the locking tongue (85) is perpendicular to the sliding direction of the sliding engagement structures. After the sliding engagement structure pairs move relative to each other and are in position, the locking tongue (85) contacts a stop face (103) of the battery holder, so that the sliding engagement structure pairs are locked.
