If you try to open laravel built in web server using other computer on the same network, it won't work, don't worry there is a solution to this problem.
All you need to do to make the built in web server accessible through network is running special command along with php artisan serve.
php artisan serve --host 0.0.0.0
php artisan serve --host 0.0.0.0 --port=9999
Now the built in web server should be accessible on the network, go ahead try it, remember to use real ip address of the computer instead of localhost or 127.0.0.1.
For example my computer have ip address 192.168.43.236, so i open http://192.168.43.236:8000 to open laravel built in web server, it should works.