Method for manufacturing electron source and image-forming apparatus

A method for manufacturing an electron source includes an activation operation for repetitively applying a pulse voltage to a plurality of electron-emitting devices in an atmosphere containing an organic material to form a film containing carbon from the organic material existing in the atmosphere. An activation operation is divided into a plurality of steps from a first activation step to a final activation step, with the plurality of electron-emitting devices being divided into operation units each comprising a plurality of device groups, each of which includes a plurality of electron-emitting devices. The first activation step of the activation operation is sequentially executed from an arbitrary operation unit wherein, in the first activation step, a pulse voltage is applied to each of the plurality of groups sequentially, and the sequential applying of the voltage is repeated. The first activation step for all of the operation units is terminated, and after that, the plurality of electron-emitting devices are divided into operation units each comprising a plurality of device groups, each of which includes a plurality of electron-emitting devices. A next activation step for all of the operation units is terminated in a manner similar to the first activation step, and such a procedure is repeated until the final activation step.