a syringe kit for mixing two medicinal fluids includes first and second barrels adapted to contain medicinal fluids therein . the first barrel includes a connecting tube portion at a tip portion thereof having a male screw on an outer periphery , and an inner tapered surface on an inner periphery . the second barrel includes a nozzle portion at a tip portion thereof having a screw tube portion with a female screw on an inner periphery thereof freely engageable with the male screw , and an outer tapered surface fitting to the inner tapered surface on the inner periphery . at least a surface of the male screw and the outer periphery of the connecting tube portion of the first barrel , or a surface of the female screw and the inner periphery of the screw tube portion of the second barrel are roughened to a surface roughness in a range between ra1 . 0 and ra2 . 0 .