A device manufacturing method includes a first exposure step for executing a multiple exposure of a first layer of a substrate by use of plural first masks, a development step for developing the first layer of the substrate and a second exposure step, executed after the development step, for executing a multiple exposure of a second layer of the substrate by use of plural second masks. A portion of at least one of the first masks has a pattern the same as a pattern formed in a portion of at least one of the second masks.