The purpose of this study is to demonstrate eye movements associated with piano sight-reading errors. A musical piece with wide leaps - which often lead performers into errors - were used to clarify the following four areas : (１) the line of sights during the performance, (２) the presence of errors, (３) the timing of checking the keyboard and (４) eye movements during performance errors. In most cases, before playing wide leaps, both the experts and intermediates looked down at the keyboard so as to prevent errors. In case without an error, the experts looked down at the keyboard 0.8-1 beat ahead while the intermediates 0.6-1 beat ahead. The intermediates often looked down at the keyboard while also extending the length of the note preceding wide leaps. The experts made almost no errors although the intermediates made many errors. Approximately half of their reactions to the error were to play again. The number of the intermediates who check the score before playing again is more than that the keyboard. It suggests an early look at the keys on the keyboard helps to prevent errors.