Provided is a microchip having a liquid supply mechanism which can supply a solution in a micro flow path with a simple construction in which a drive source utilizing an osmotic pressure is arranged within the microchip and which controls the osmotic pressure by a control unit utilizing temperature or the like, whereby it is possible to effect drive control such as intermittent driving and continuous driving at a fixed velocity. The liquid supply mechanism using osmotic pressure includes an osmotic pump utilizing the osmotic pressure of a liquid filling chambers separated from each other by a semipermeable membrane, and a unit which varies the osmotic pressure by changing a condition of the solution in at least one of the chambers on the basis of a timing of a pumping operation.