The female witness has told police she saw a man leaving Ballarat and Clarendon College with two laptop computers about 9am.

The witness, a parent at the school, noticed the man and followed at a discreet distance and called school staff.

Information about the suspect's actions and location was then relayed to police.

Detective Senior Constable Steve Howard said the man fled police when they arrived at the scene.

Det Sen Const Howard said the man tried to hide in a Gnarr Creek ditch near the Ballarat Home Brew Centre in Ripon St Sth.

Ballarat uniform and CIU police found and arrested the man about 9.20am.

Det Sen Const Howard said the witness's quick thinking was vital in finding and arresting the suspect.

"We probably never would have seen the laptops again," he said.

Det Sen Const Howard said this was the right thing to do and warned others from approaching people they suspect had committed a crime.

"Keep them in view (and keep in contact with police) and it gives us a better view of where the perpetrators are."

The man has been charged with two counts of theft and was remanded in custody yesterday afternoon without making any application for bail.

He will reappear at Ballarat Magistrates Court today.

Meanwhile, police are investigating the theft of more than $700 of goods from a car in Lydiard St Nth shortly before 7am yesterday.

Anyone who has any information about these or other crimes can contact Ballarat Police on 5336 6000 or Crime Stoppers on 1800 333 000.