Doesn't delete files if exists from public folder | Laravel 5.7

I am using Laravel app with Intervention Image. However, if i upload a new image, old images will not be deleted. I'm writing a controller as follows.

//user image
        $image_icon = $request->file('image_icon');
        if($image_icon) {
            \File::delete(public_path() .'/upload/user/'.$user->image_icon.'-b.jpg');
            \File::delete(public_path() .'/upload/user/big'.$user->image_icon.'-s.jpg');
            $tmpFilePath = 'upload/user/';
            $tmpFilePathBig = 'upload/user/big/';
            $hardPath =  str_slug($inputs['full_name'], '-').'-'.md5(time());
            $img = Image::make($image_icon);
            $img1 = Image::make($image_icon);
            $img->fit(270, 225)->save($tmpFilePath.$hardPath.'-b.jpg');
            $img1->fit(360, 360)->save($tmpFilePathBig.$hardPath.'-s.jpg');
            $user->image_icon = $tmpFilePath.$hardPath;
        } 

Now i have doesn't work File::delete method. There is no file upload error. But the old image is not removed. How can i fix this problem? Thanks!