I have been led to believe that yes, it does, which is a waste of power. I always unplug ours when not in use. OH thinks differently, that it's only using power when the phone's attached.
About as little as leaving a small extension cord plugged in with nothing connected, you'd have to have very sensitive equipment to detect the usage.
It is always safer to unplug any unused item though. Many housefires are started by unused item being left 'live'.
Your question has been answered but you might be surprised to find out just how many devices are still using electricity even when you think that they're switched off. For example, when your printer is switched off, put a portable radio next to it and note the buzzing or whistling sound that will almost certainly be heard. That shows that components inside it are still powered up (and adding to your electricity bill). The only way to stop that happening is to unplug the printer from the mains.
Many other devices still use power when they're switched off (and some TV sets use almost as much power on 'standby' as they do when they're switched on).
There are now adaptors on the market that you can use to charge your mobile phone that cut off when the phone is fully charged, (available from the Electric Companies) seems a good idea to me, does two jobs saves electric and prolongs the phone battery life.
No doubt I'll be accused of not having actually worked out the figures, but I suspect worrying about a little extra cost of things plugged in and not operating is rather over the top. The small amount of power used will heat your home anyway, and the convenience of, say, knowing the battery is charged when you take it, must be worth something. If you are going to be worried about something, worry about a fault developing and the item getting hot and bursting into flames :-)
The Scottish government went to the expense of running TV ads advising that all such charger devices should be unplugged, or at least switched off at the main, when not in use. They've been known to overheat, and thus can create a fire risk. Never mind how little electricity they use when not charging, unplug or switch off.