Does a bed frame like this need a box spring?

No a bed frame like that wouldn't need a box spring, if it has wooden slates that sit in the frame of the bed design. The wooden slates would hold the bed within the bed frame. the whole point of the bed its to be slightly lifted off the floor.

No...just the mattress!

I LOVE platform beds! Check out ikea's platform beds if you are looking for a cheaper price

This bed uses a panel underneath..it says shipped READY TO ASSEMBLE..meaning, no this one doesn't..I was reading a couple other naswers..this bed does not need slats either..one said slates..but slats was meant..the description says it has PANELS..not slats

if the mattress has a spring in it, then you wouldnt need a box spring.

I would think so unless it is temperpedic