A production method of a micromachine includes a polysilicon film forming step which overlays grooves, defined in an upper surface of a sacrificial layer on a silicon substrate, with polysilicon layer so as to be flat. The production method includes a first processing step for filling the grooves by adding a lower laid portion of the polysilicon layer onto a sacrificial layer. The lower laid portion has a thickness greater than 0.625 times relative to a width of the grooves. The production method of the micromachine further includes a second processing step for making the polysilicon layer to have a predetermined thickness by adding a upper laid portion of the polysilicon layer on the lower laid portion to form the polysilicon layer, the upper laid portion formed by depositing polysilicon which has the same impurity concentration as the lower laid portion does.