The present invention relates to a cell culture assay. The present invention comprises: a substrate; a scaffold channel which is formed along the centre inside the substrate, and of which at least one is disposed continuously, and inside which a scaffold flows; and a microfluidic channel or channels which is/are respectively formed on one side or on both sides of the scaffold channel, and inside which cells flow, and, here, a leak-preventing part for preventing the scaffold from leaking into the microfluidic channel(s) is formed in at least one of the ceiling surface and the floor surface of a boundary part of the scaffold channel and the microfluidic channel(s). In this way, because the leak-preventing part extends over the ceiling surface or the floor surface of the boundary part of the scaffold channel and microfluidic channel(s), the present invention has the advantages of allowing cell culturing to be observed and accurate quantification to be performed during reactions without the cells reacting with other structural elements and detritus, and of allowing cell interactions to be studied.