1. A named-entity detection apparatus comprising: a candidate-named-entity extraction module detecting a candidate-named-entity based on an initial learning example and feature information regarding morphemes constituting an inputted sentence, the candidate-named-entity extraction module providing a tagged sentence including the detected candidate-named-entity; a storage module storing information regarding a named-entity dictionary and a rule; and a learning-example-regeneration module determining whether the candidate-named-entity included in the provided sentence is a valid named-entity, based on the named-entity dictionary and the rule, and providing the sentence as a learning example, based on a determination result, so that a probability of named-entity candidate detection is gradually updated.