Can I use my power cable which I use in Belgium in Beijing? Or would I need a converter?

In Belgium, it is British-standard socket, therefore, you need a converter in China.

Thanks for the answer.

Does this adapter needs to be a converter as well to provide the correct voltage (i.e. change 220V to 110V or something like that)? Or just a regular adapter to change my socket to the "Chinese socket" would be enough?

You just need a regular adaptor.

Fyi,

Although I've found a regular adapter as suggested and took it with me, I didn't need to use it.

My travel was to Beijing. In the hotel, the office building, and the airport all sockets were compatible with the standard European plugs.

I assume it can be different on other places/parts.