The present invention provides a method and apparatus for starting an engine which can decrease the amount of compressed air consumed by air motors and can lessen an increase in a size of a compressed air tank and an increase in a size of an air compressor, and in a method of starting an engine using a plurality of air motors, the number of air motors being operative is decreased before the engine can start increasing its engine speed for itself, at starting. That is, during increasing of the engine speed of the engine at the starting, the number of air motors being operative is decreased from, for example, two to one.