Can an Indian passport holder having 10 yr multi entry visa to US?
Holding a B1/B2 US Visa allows us to visit only USA. To visit Canada, you must apply for a Canadian Visit Visa which would be issued by Canada. You can apply using the information available here - Apply for a visitor visa Answer to the Question : Do I need a Canadian visa if I have a United States visa? Yes, most travellers need a visitor visa or an eTA to travel to, or transit through, Canada. What you need depends on: the type of travel document you will travel with; the country that issued your travel document; your nationality; and how you will travel to Canada. Source - Do I need a Canadian visa if I have a United States visa?