Upgrade laravel to version 5.7

I want to upgrade laravel to 5.7 version.When I type

php artisan --version It shows Laravel Framework 5.4.36

In composer.json file I had put

"require": {

"php": ">=7.1.3",
"laravel/framework": "5.7.*",
"laravel/tinker": "~1.0"
}

but version not updating. To update I use

composer update
Kindly suggest.

via Chebli Mohamed