adverb
in everything; in every matter; on every occasion
Used to express that something happens or is done in each and every case, often with a nuance of thoroughness or without exception.
彼は事ごとに文句を言う。
He complains about everything.
事ごとに準備を怠らない。
I never fail to prepare for every single thing.
Similar meaning of 'in every matter', but 何かにつけて is more about taking every opportunity, while 事ごとに emphasizes each individual matter or case.
Compound of 事 (こと, 'thing, matter') + 毎 (ごと, 'every') + に (particle). The reading ごと is a rendaku form of こと.