An image processing apparatus that can transmit an image outputted after the execution of a workflow as well as an attribute information file including attribute information suitable for an external system as a transmission destination to the external system. An attribute information management unit manages attributes required by the external system when the image data is transmitted to the external system. A workflow execution unit executes a workflow as a sequential processing in which a plurality of functions of the image processing apparatus are combined. An attribute value setting unit sets attribute values for the attributes required by the external system when the communication unit transmits the image data to the external system. An external system interconnection unit causes the communication unit to transmit the image data output from the workflow execution unit to the external system with reference to the attribute values set by the attribute value setting unit.