To automatically and efficiently bind thick reinforcements for a foundation or a retaining wall with a thick binding wire.

This automatic binding apparatus 1 comprises: a main body section 2, the upper portion of which is provided with holding portions 6 and 7 and the lower portion of which is provided with a rolling mechanism 5; a binding-wire feeding section 3 which is provided on the front side of the main body section 2; a driving section 4 which is equipped with a motor provided on the backside and capable of selectively running in normal and reverse directions; and first-third drive transmission means which are driven by the driving section 4. A crossing portion between the reinforcements 70 and 71 to be bound is interposed between the binding-wire feeding section 3 and the rolling mechanism 5. The crossing portion between the reinforcements is held by the single binding wire which is pushed out by a pushing means; and a leading end of the binding wire holding the crossing portion is engaged with a rolling member 57 of the rolling mechanism 5, and twisted a plurality of times. Even if the binding wire with a thickness exceeding 2.5-3 mm and having a high rigidity can be used, efficient and safe winding work can be executed.