A developing agent for electrophotography which comprises toner particles containing a resin binder and a colorant. The toner particles include which have diameter of 5 .mu.m or less and which account for less than 10% by number of all particles, and include particles which have diameter of 20 .mu.m or more and which account for less than 0.5% by weight, and the weight average standard deviation in particle diameter of the toner particles is 2.5 .mu.m or less. The developing agent may further contain an external additive comprising small silica particles 6 nm to less than 18 nm in average primary particle diameter and large silica particles 18 nm to less than 46 nm in average primary particle diameter.