The present invention provides microfluidic channel structures to provide a uniform concentration gradient according as the mixture of two or more fluids. The present invention for this purpose is a circular cross-channel structure comprising a circular channel, and the circular channel and fluid inlet channel, outlet channel and each symmetrical pair of the branch channel connected to the fluid to move the fluid inlet channel to the circular channel and radially connected with the discharging channel is radially connected to the fluid inlet channel and the opposite direction with respect to the circular channel, the pair of branch channels is greater than the extension and 0 ° to the fluid flow direction of the fluid inlet channel 90 of each of the yirumyeonseo ° less than that formed by each branch from the contacts in contact with the circular cross-channel, one provides a circular cross-channel structure having the mixed fluid a uniform concentration gradient in the channel. The present invention can be branched uniformly mixing them in the flow according to the present invention, three or more fluids.