Yidake, advertising your eBay auctions is not a problem at all so far as policy goes - but it does call for real care on your part as the advertiser.
Specifically, you really need to be on top of when your AdWords ad is running relative to the limited period of time during which the auction is running.
So, assuming you mean that you want to advertiser individual items, you must not set your AdWords ad running before the auction has started, and it must not run after the auction has ended. Either case would be a less-than-desirable user experience.
Also, to look at another scenario, if you intend to link to the page on which all your items are listed, then an item related to your ad must be available there during the entire run of your ad.
Hope that makes sense.