There are provided a guide wire, a medical device, and a medical method which can achieve satisfactory workability and can ensure safety by preventing a puncture needle portion from performing erroneous puncture.A guide wire (10) for guiding a dilator (40) to be inserted into a living body includes a shaft portion (11), a puncture portion (15) fixed to a distal portion of the shaft portion (11), and whose distal side includes a needle portion (16) for forming a hole in a biological tissue, and a deformable deformation portion (30) fixed to the shaft portion (11) or the puncture portion (15). The deformation portion (30) located inside the dilator (40) restricts deflection of the distal portion of the shaft portion (11).
