Provided are a pile joint, a pile coupling structure, and a pile coupling method that allow firm uniting of piles to be coupled. A joint (10) for coupling two piles (12) comprises: a tubular body (16) into which each pile (12) provided with a key (14) on a periphery thereof is inserted through an end (16A) of the body (16); and a fitting portion (22) formed on the body (16) so as to be fitted to the key (14) by the insertion and rotation of the pile (12). The fitting portion (22) is formed with: a tapered shape having a surface (22A) that is inclined so as to become distant from the end (16A) of the body (16) as the surface (22A) extends in the direction of rotation of the pile (12); or a wedge shape for fitting between a projection and a pile.