How do experts differ from novices in knowledge domain of second language? The purpose of this study was to investigate the differences of experts and novices in general knowledge and metaknowledge of second language vocabulary. Subjects were required to produce both Japanese (as a first language) and English (as a second language) abstract words by reading Japanese or English sentences which defined those words. When subjects could not produce English words, they were asked to make a "feeling of knowing (as metaknowledge)" judgement on a scale from 1 to 10. The results showed that second language experts were superior to novices in both general knowledge and metaknowledge: (a) concerning general knowledge, experts were able to retrieve more easily not only second language words but also first language words, and (b) concerning metaknowledge, experts were able to rate more exactly the feeling of knowing for knowledge of second language vocabulary.