1. A method of generating a mashup graph, the method comprising: receiving a set of services and collecting application programmable interfaces (APIs) of the services; generating a mashup graph by using the collected APIs, according to information regarding connections between the APIs and weights between the APIs; and reflecting a user's request to the mashup graph, and generating and outputting a mashup list, wherein, when the user's request comprises a category, a virtual node corresponding to the category is generated, a mashup list is generated using a minimum spanning node including the virtual node, wherein each of the weights reflects at least one of a user's frequency of use of a service, a general frequency of use of a service and a recommended value of a service, and wherein the generating the mashup graph is performed by a processor.