To provide a micro-analysis chip having extra fine grooves formed by using a film-shaped photoresist, its manufacturing method and an analyzer such as a device for capillary electrophoretic migration using the same.

In this method of forming the ultra fine grooves by using the film-shaped photoresist, a micro analysis chip and its manufacturing method is characterized by including the same kind of molecular structure part in at least one set of an insulating base and the photoresist, or the photoresist and a seal member, when the seal member is adhered to the ultra fine grooves manufactured by closely adhering the film-shaped photoresist onto the insulating base, and then exposing and developing the film-shaped photoresist.