It's hard to find the opening hours to the DPRK embassy in Beijing if you search the web. These are the opening hours as of 2014:
Monday and Friday - 9:30-11:30 a.m., 2:30-5:30 p.m.
Tuesday, Wednesday, Thursday - 9:30-11:30 a.m.
Rumors have it that the embassy's consular section is sometimes open on Saturday morning, but not always.
The embassy's consular section is located in Cao Fang Di, between the Utown and Parkview Green malls.