Provided are an active-matrix substrate having a reliable line connection structure, a method for producing the same, and a display device including the same.A first metal line 122 and a second metal line 125 are electrically connected via an IGZO layer 124 rendered conductive. In this case, the second metal line 125 is isolated from an ITO layer 109 without contacting the ITO layer 109 because there are a passivation layer 107 and an organic insulating film 108 formed between the second metal line 125 and the ITO layer 109. Thus, no contact fault due to electric corrosion occurs between an aluminum layer 125a of the second metal line 125 and the ITO layer 109, whereby a reliable line connection structure is achieved.