Could you just ask you office manager or the IT helpdesk? Unless it's against company policy, they should be able to give it to you. If not, you can probably find it a couple of other ways.
You could simply look at the router for the key, unless the default password has been changed. Obviously, this depends on the office, but in a small business the router is usually just sitting on top of a filing cabinet or attached to a wall, If you can physically access it, look for a sticker with the network key/password.
Another pretty simple way is to check on your PC. Again, this depends on your office and how tightly your admin has restricted user access, but if it doesn't require admin access this is pretty easy. For Windows 8:
1. Right-click on the WiFi symbol in the systray and select Open Network and Sharing Center.
2. Click Change adapter settings.
3. Right-click the WiFi adapter icon.
4. In the WiFi Status dialog click on Wireless Properties.
5. Click the Security tab and then check the box to show characters.