In a statement, Chief Executive Officer Pierre Karl Peladeau said the move was a difficult decision.
"This restructuring is regrettable but warranted by changes in our industry which force us to align our cost structure with the new reality," he said. "We very much regret the impact that this has on employees who are departing our organization and would like to thank them for their contribution."
The company, a subsidiary of Quebecor Media Inc., said it would be closing two printing plants in Ottawa and Kingston, both in Ontario.
Sun Media's website said it is Canada's largest newspaper publisher based on circulation of paid and free newspapers.
It publishes more than 15 million copies each week that include 36 paid-circulation daily newspapers and six free dailies in nine of the 10 largest urban markets in Canada, the site says. It also runs nearly 200 community newspapers as well as English and French television networks.