Can I submit an app without iPad version to App Store? I finished an app a while ago but this app's layout only works well in iPhone and I didn't plan to let it available for iPad, I just want it to work on iPhone devices.

Is it possible to submit to App Store and iPhone app that won't be available for iPad?

At iTunes Connect -&gt; My Apps -&gt; (App Name) -&gt; App Store -&gt; iOS APP -&gt; Prepare for submission I didn't see anything like permitted devices.
No, you can't prevent an iPhone app from being installed on an iPad.  You can prevent an iPad app from being downloaded to an unjailbroken iPhone.  As mentioned in the comments, an iPhone app can run on an iPad in 'compatability mode'.  

Your app should still look ok on an iPad unless your setting up autolayout constraints based on specific iPhone screen sizes.  One of the benefits of autolayout is that your app should be able to run on different screen sizes, including iPads.

You would need to indicate in the App Store description that this app is not designed to run properly on the iPad. I would recommend spending the time to make it look decent on the iPad knowing that people will still download it on their iPads regardless of what you state in the description.