I've carried small rice cookers, tea kettles and travel cookpots through security multiple times. Just make sure that you leave plenty of time for extra security screening. I would carry-on if possible since I've found that TSA tends to just toss things back in your checked bag without a thought as to how it was packed in the first place. If your mini rice cooker is the type that has a lot of nesting bowls, lids and latches, chances are the TSA won't put it back together properly.

As mentioned above, there is always the microwavable rice cooker if you have access to a microwave.

If you're travelling internationally, make sure to check to bring both a voltage converter and a plug converter.