A manufacturing method is provided which can improve the heat resistance of an interposer using a glass substrate. The interposer manufacturing method comprises manufacturing a plurality of interposers from a material substrate including a glass substrate partitioned by a plurality of crossing division lines to define a plurality of separate regions and a stacked member provided on the first surface or the second surface opposite to the first surface of the glass substrate, the stacked member including an insulating layer and a wiring layer, the interposer manufacturing method including a cutgroove forming step of cutting an exposed surface of the stacked member along each division line by using a first cutting blade to thereby form a cut groove on the exposed surface of the stacked member, the cut groove having a depth not reaching the glass substrate; and a dividing step of cutting the glass substrate along each cut groove by using a second cutting blade having a thickness smaller than the width of each cut groove to thereby divide the glass substrate and manufacture the plurality of interposers.