1. A voice recognition device that recognizes a voice uttered by a user and displays an operation button to which a function corresponding to a recognition result is assigned, said voice recognition device comprising: a voice acquirer to detect and acquire a voice uttered by said user; a voice recognizer to refer to a voice recognition dictionary, recognize voice data acquired by said voice acquirer, and output a recognition result; a display to display an operation button to which a function corresponding to the recognition result outputted by said voice recognizer is assigned; a display controller to output a command for displaying the operation button to which the function corresponding to the recognition result outputted by said voice recognizer is assigned in a recognition result display area of said display; a display priority calculator to calculate a display priority for said operation button corresponding to said recognition result, said display priority indicating a degree that said operation button should be displayed in preference to information other than said operation button in said recognition result display area, said display priority for said operation button corresponding to said recognition result being calculated to reflect whether display of said operation button would distract from other display information that would be important to the user; and a recognition result output controller to increase a display frequency of said operation button with increase in the display priority calculated by said display priority calculator by decreasing an output frequency of said information other than said operation button, wherein said voice recognition device is applied to a navigation device that displays a map on said display and provides route guidance for a moving object, and said display priority calculator calculates said display priority on a basis of a positional relationship between a traveling direction of said moving object displayed on said display and said recognition result display area, such that said display priority calculator decreases display priority for said operation button corresponding to said recognition result when the traveling direction of said moving object is aligned with said recognition result display area.