The suspect, who is Chinese and in his 30s, was taken into custody after police spotted him on the rooftop of a building next to the scene of Saturday night's attack, the South China Morning Post reported.
Police also found bottles believed to contain acid that was hurled onto the busy Temple Street night market, a pedestrian shopping district frequented by tourists, the report said.
Among the injured were nine tourists and a seven-year-old, the Post said, adding that all the victims have since been treated in hospital and released.
Police would not say if the man taken into custody is connected to five previous acid attacks in Hong Kong since late 2008.
Three took place in densely populated Mong Kok, a shopping district near the scene of Saturday night's attack.
Last month six people were injured when a bottle of acid was hurled down a street in Causeway Bay, another shopping hub which was packed with people celebrating the Hong Kong football team's victory over Japan in the East Asian Games final.
Police could not immediately be contacted for comment.
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