Its upside down. It reads 成化年造 which might be read Seika Nenzō (kanji have different possible readings). However, when I put these four kanji into a search engine, all that comes up is similar-looking pottery, all from Chinese auction sites.
成化 originally refers to a period of the Ming dynasty in China (1465~1487). Porcelains in this era is very famous, so this seal has been used to show "good quality" even after that, not only in China but also in Japan. Thus, 成化年造 or 成化年製 doesn't prove that it's made in that era at all.