1. A navigation system for executing a guidance with a screen display or speech, comprising: a controller that generates the guidance depending on a state of a movable body with the navigation system mounted thereon; and a user interface that receives supply of the guidance generated by the controller to thereby output the guidance with a screen display or speech to a user of the navigation system, wherein if the controller has a plurality of the guidances as generated, the controller determines a method whereby the user interface outputs a screen display or speech according to an execution condition set depending on the type of a relevant guidance.