A handlebar structure of bicycle suited for being assembled to a stem of a bicycle is provided. The handlebar structure includes a body and a reinforcement member. The body has a first segment fixed to the stem, a second segment, and a third segment held by a rider, wherein the second segment is connected between the first and the third segments. One portion of the reinforcement member is fixed to the stem, and another portion of the reinforcement member is disposed on the second segment. A two-dimensional Cartesian system x-y based on an orthogonal cross-section of the second segment is constructed, and a scope of the second segment being covered by the reinforcement member contains at least a second quadrant of the two-dimensional Cartesian system x-y, wherein the bicycle moves in a positive x-axis direction of the two-dimensional Cartesian system x-y.