这是关系到你的SSL设置，可能它不是（* .domain.com）设置如果是这样（www.domain.com）没有问题任何错误。

www.domain.com！= domain.com

由于 WWW 的子域，即重定向到（ domain.com ），那么，你需要启用SSL对（ *。domain.com ），或者只是为（ www.domain.com ）所建议的@Jack

I have a website with the ssl for www.example.com. I have set up a htaccess redirect which redirects the user from http://example.com => http://www.example.com. If I enter https://www.example.com then it works. But if I enter https://example.com then it gives me a ssl error.

How do I redirect https://example.com to https://www.example.com without showing the ssl error?

I use the following code in my htaccess to redirect.

RewriteCond %{HTTP_HOST} !^www\.

RewriteRule ^(.*)$ http://www.%{HTTP_HOST}/$1 [R=301,L]

This is related to your SSL setup, probably its not set for (*.domain.com) if so (www.domain.com) doesn't issues any error.

www.domain.com != domain.com

Because www is subdomain, that redirected to (domain.com), then, you need to enable SSL for (*.domain.com) or just for (www.domain.com) as suggested by @Jack