"php artisan serve" have error

Hello my friends, i try to use laravel on ubuntu. composer installed successfully and command "composer create-project --prefer-dist laravel/laravel blog", my project folder created successfully too, but when i run it with "php artisan serve", I have this error:

PHP Fatal error: Uncaught Error: Class 'Illuminate\Foundation\Application' not found in /home/javad/Desktop/blog/bootstrap/app.php:14 Stack trace: #0 /home/javad/Desktop/blog/artisan(18): require_once() #1 {main} thrown in /home/javad/Desktop/blog/bootstrap/app.php on line 14

I searched about this everywhere but there was no result :(

Help me please.