Vehicle side-door structure

A vehicle side-door structure, in which a front door (2) and a rear door cover a continuous opening with no partition in a side part of a vehicle so that the opening is opened and closed, the front door (2) is pivotally attached on a hinge at its front part to a vehicle body so that the front door (2) is opened and closed, and the rear door (3) is pivotally attached on a hinge at its rear part to the vehicle body so that the rear door is opened and closed, includes: a front-door rear reinforcement, the front-door rear reinforcement (31) being disposed at a rear end part of the front door and extending in the vertical direction along the rear end part.