Children's conception of lies has been important issues for children's cognitive development. However, little is known about whether children's understanding of lies is different form adults' one. Four kinds of stories were presented for children aged 6- to 7- year olds and undergraduate students. First, a protagonist had a deceptive intention and produced a false statement. Second, he had a deceptive intention but produced a true statement by a false belief. Third, he had a truthful intention and produced a true statement. Fourth, he had a truthful intention but produced a false statement by a false belief. The results showed that undergraduate students judged that these protagonist's statements were lying or not by considering his intentions. By contrast, children judged regardless of his intentions. These results suggest that children's conception of lying is different from adults' one, and that their conception becomes sophisticated after middle childhood.