A method includes providing an indwelling tool having a magnetic body at the inside of a luminal organ by inserting the tool into a working channel inserted from a natural opening of a living body to the luminal organ, in a manner such that an axis along a length of the magnetic body is arranged substantially parallel to a length direction of the working channel; disposing the tool in a vicinity of a diseased part of the luminal organ; applying a magnetic field to the magnetic body by using a magnetic field generating device provided at the outside of the luminal organ, so as to attract the magnetic body and make a side face of the magnetic body along the axis thereof push against a tissue in the vicinity of the diseased part; and lifting a tissue around a position of the tool, which includes the diseased part, by applying a magnetic force to the magnetic body by using the magnetic field generating device.