Tourists who want to enter in Hong Kong might need to apply for a visa according to the regulation of Hong Kong visa system, because the visa system in Hong Kong is different from that of China mainland.
Generally, a valid entry on your Chinese visa should be carried by you if you enter Hong Kong from the China mainland and return, or you can apply a new visa in Hong Kong (and although it is normally granted, it is not a 100% certainty).
Visitors staying in Hong Kong within 14 days to 90 days, depending on which passport you are holding, is allowed without visas. But sufficient funds are one of the pre-conditions because Hong Kong Government will not allow any visitors to look for a job here even without paid.
Hong Kong Visa Exemption
Not all the people who travel to Hong Kong need to get tourist visas. Visitors who carry the following documents can enter into it without visas:
Hong Kong Special Administrative Region Passport
British National (Overseas) Passport
Hong Kong Certificate of Identity
Hong Kong Re-entry Permit (for entry from the Mainland of China and the Macao Special Administrative Region only)
Hong Kong Permanent Identity Card
Hong Kong Seaman's Identity Book
Any travel documents bearing one of the following endorsements: "Holder's eligibility for Hong Kong permanent identity card verified" or "The holder of this travel document has the right to land in Hong Kong.
The detailed information about people who should apply for a Hong Kong visa can be found in the Hong Kong Immigration Authority’s website.