Hiding the SSID is not the best thing to do if you want to avoid visitors from connecting it. They can guess the SSID or find another way to connect to your router.
My recommendation is to set a strong password to your router so that only those who have the password will be able to connect. Another solution to secure your router is to enable the MAC filtering to prevent unwanted access. Only authorized devices with their adresses listed in the router's filtering page will be able to connect.