After a second plate member 3 is inserted into a space which is surrounded by side walls 6a through 6d of a first plate member 2, the bonded surface 3a of the second plate member 3 is bonded and fixed to the bonded surface 2a of the first plate member 2 by an adhesive to form a sample handling unit 1. At this time, the second plate member 3 is positioned by protrusions 35 and 36 of the first plate member 2 in X and Y directions, and positioned and fixed by holding members 8 through 13 and inside holding members 26 and 27 in Z directions (normal directions on an external surface 7). A microfluidic device 101 includes microchips 106 through 108 of plural kinds having passages 132 through 134 for transporting a sample, and a base member 102 on which the microchips 106 through 108 are arranged. After the base member 102 and the microchips 106 through 108 are separately formed, microchips 106 through 108 of kinds necessary for intended purpose, such as analysis of the sample, are selected to be suitably combined to be positioned and fixed on the base member 102 to form the microfluidic device 101. By causing the positioning holes 127 of the microchips 106 through 108 to engage the positioning protrusions 128 of the base member 102, the microchips 106 through 108 are positioned with respect to the base member 102.