sets a contrast.
"in addition, (...)", "and on top of that, (...)"
それに、彼は家事もしないんでしょう？ On top of that, he doesn't do house chores either, right?
昨日、道で千円を {拾|ひろ}って、それに車が抽選で当たった。 Yesterday, I found 1000 yen on the street. In addition, I (also) won a car in the lottery.
最近は雨がいっぱい降るし、それに風も強いし、そとに出れなくて寂しい。 Because recently it has been raining a lot, and in addition to that the wind has (also) been strong, I am not able to go outside and am therefore sad.