A syringe kit for mixing two medicinal fluids includes first and second barrels containing medicinal fluids therein. The first barrel includes a connecting tube portion at a tip portion having a male screw on an outer periphery, and a non-roughened inner tapered surface on an inner periphery. The second barrel includes a second plunger, a screw tube portion with a female screw on an inner periphery thereof freely engageable with the male screw of the connecting tube portion, and a nozzle portion situated inside the screw tube portion with a non-roughened outer tapered surface fitting to the non-roughened inner tapered surface. A surface of the male screw and the outer periphery of the connecting tube portion, or a surface of the female screw and the inner periphery of the screw tube portion are roughened to a surface roughness in a range between Ra 1.0 and Ra 2.0 micrometer.