To manufacture a micro-chip without polishing joining faces of glass substrates for constituting the micro-chip to make them an optical plane.

This micro-chip 100 has a base plate 2 comprising the glass substrate 6 formed with a yoked type groove 1 branched respectively in its both ends on one side face, and a cover plate 4 comprising the glass substrate 7 joined to one side face of the base plate 2. The cover plate 4 has four through holes 3 for sample injection and discharge in positions corresponding to the groove 1. The groove 1 constitutes a micro-passage 5 for the micro-chip 100. The glass substrate 6 and the glass substrate 7 are different each other in their temperature-viscosity curves. The micro-chip 100 is manufactured by joining the glass substrate 6 and the glass substrate 7 while heating them at a prescribed temperature.