Providing a method for forming an opening of a shape precisely matching the stoma of a patient in a base plate of a stoma device. A method of forming an opening in a base plate of a stoma device according to the present invention comprises a step of printing on a label a filled-in-part of the same shape as a hole of a shape formed on a template sheet and matching the stoma of a patient, a step of sticking the label on which the filled-in-part has been printed on to a base plate, and a step of cutting the base plate along the contours of the filled-in-part of the label stuck to the base plate.
