Error on deploying with Git on Heroku

I’m not able to deploy in Heroku. I’m getting Permission Denied! everytime. I have my repository already exists.

$ git remote -v
heroku  git@heroku.com:catapp11.git (fetch)
heroku  git@heroku.com:catapp11.git (push)

But while I try to push in Heroku, I always get error.

$ git push -u heroku master
Permission denied (publickey).
fatal: Could not read from remote repository.

Please make sure you have the correct access rights
and the repository exists.

Git Baby is a git and github fan, let's start git clone.