China Visa Question.

I am Singapore citizen. I will going to ShenZhen for 14 days , then I will visit Hk for 1 day before heading back to Shenzhen for another 14 days and back to Singapore after that. Do I still need to apply for Visa? Thanks. Day 1-14 Shenzhen. Day 14 morning go to HK and return back at night. Stay another 14 days and come back to Singapore