A police spokesperson told the BBC that the suspect was the same man who stabbed three people at the parade in 2005.
Yishai Schlissel, an ultra-Orthodox Jew, was sentenced to 12 years in prison for that attack and was released from prison three weeks ago.
Two of the injured are in a serious condition, the ambulance service said.
Eyewitnesses told Israel’s Haaretz newspaper that the attacker emerged behind marchers and began stabbing them while screaming, before being tackled by a police officer.
The march has long been a source of tension between Jerusalem’s secular majority and its Jewish Orthodox communities.
Hundreds of police are deployed along the route to try to prevent violence breaking out.
Ultra-Orthodox Jews have previously gathered in the city’s Mea Shearim quarter to protest against homosexuality.
By:3news.com/Ghana
Jerusalem Gay Pride: Six stabbed 'by ultra-Orthodox Jew'
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Police have arrested a man after six people were wounded in a stabbing at the Gay Pride parade in Jerusalem.