A navigation system comprises a detection part for detecting a location and a speed of a navigation apparatus, a voice message weight storage part for storing voice message weight association information, which associates a weight with each of multiple voice messages, a rule storage part for storing priority rule information denoting a rule for deciding a priority for each of multiple voice messages, a priority decision part for deciding a priority for each of the multiple voice messages based on the priority rule information, and a voice output part for outputting from the navigation apparatus multiple voice messages in a sequence conforming to the decided priority. The rule denoted by the priority rule information is a rule for deciding the priority for each voice message based on the detected location and speed of the navigation apparatus, and the weight of each voice message denoted by the voice-weight association information.