Háizi chūshēng hòu, tā cízhí dāng le quánzhí bàba.
After the baby was born, he quit his job to be a stay-at-home dad.
Tips
usage
全职 goes before a noun, 全职工作 'a full-time job', or before a verb, 全职写作 'to write full-time'. The opposite is 兼职 'part-time'. A stay-at-home mother is a 全职妈妈 or 全职太太.