Dear Abhishek, you are just confusing yourself over direction of vectors...

 

As the man's acceleration is radially inwards, -ma will we in the opposite direction, and that is radially outwards....

 

because, when we take negative of a vector, its magnitude remains same, and its direction is changed by 180 degree... so opposite of radially inward is radially outwards.

 

(here centrifugal force is not just -ma... but the actual derivation is for higher classes)