A navigation device (100) has a position detection section (7), an interface (4), a touch panel (62), and a computer (1). The computer (1) has timekeeper means for clocking a current time, estimated arrival time calculation means for calculating the estimated time of arrival at a destination by using the touch panel (62), mail creation instruction means for causing, through the interface, (4) a portable telephone (200) to create mail containing text that informs arrival at the calculated estimated time of arrival, and mail transmission instruction means for causing the portable telephone (200) to transmit the created mail. The estimated time of arrival is transmitted to the other party without operation of a portable telephone by a driver.