Abstract: The present invention provides a navigation device which performs communication with an information-providing server device. The navigation device (3) includes a communication section (11) which transmits a message to the server device for a response confirmation, and receives a response message with respect to the message from the server device; a response value obtaining section (12) which determines a time duration from a time when the message is transmitted to another time when the response message is received, and obtains a response value indicating a communication state in relation to a communication time on the basis of the determined time duration; and a communication-parameter setting section (13) which determines an optimal communication parameter on the basis of the response value obtained by the response value obtaining device, and sets the optimal communication parameter in a communication parameter in relation to a communication disconnection condition used in the navigation device (3).