PROBLEM TO BE SOLVED: To provide an ion generation method by which ion species to be generated from a solid specimen is speedily changed.SOLUTION: The ion generation method includes: loading a mixed specimen into an oven of an ion source, the mixed specimen being obtained by mixing a plurality of kinds of powder specimens of which oven temperatures in the case of reaching a specific ion strength are different from each other; raising the temperature of the oven so as to generate ion from any one kind of specimen having the oven temperature in the case of reaching the specific ion strength is relatively low among the plurality of kinds of specimens; generating ion from the one kind of specimen; further raising the temperature of the oven, after the ion is generated from the one kind of specimen, so as to be such a temperature that ion is generated from any other kind of specimen of which the oven temperature in the case of reaching the specific ion strength is higher than the one kind of specimen among the plurality of kinds of specimens; and generating ion from the other kind of specimen.