I want to buy secondhand equipment but don't know which website is better, not the shop but p2p website like ebay. But there are few people sell DSLR and accessaries.

Whole load of DSLR on Ebay everyday. Just have to be careful and ask lots of questions if the deal looked suspicious or just skip it. And most importantly, the camera bought over ebay will not be covered by warranty even if it is stated as NEW, as most manufacturer do not accept item sold by non qualified reseller.

Or else you can check out Fordes https://secure.ffordes.com/index.htm
Cost a little more, but have peace of mind.

Fixing a defective DSLR can be an expensive business, by from a reputable seller.

The most important thing is not the price or warranty, but there's so few equipments in shop. And I've bought many digital things p2p. In my country, there are over 500 secondhand DSLR new showing on website for people to choose.

buying anything off websites such as ebay even if listed and proven new is no different to buying from a market stall or car boot!!!!

Most manufacturers won't honour the warranty!!!!