An electrophoresis apparatus, comprising: a sample separating section for containing a sample separating medium for separating a sample in a separating direction, the sample separating section containing the sample separating medium in such a manner that the sample separating medium has an exposed portion at one end of a surface of the sample separating medium, the surface being in parallel with the separating direction; medium connecting means (107, 108) for connecting a sample containing medium to the sample separating medium at a connecting region on the exposed portion, the sample containing medium containing a sample, and the connecting region satisfying the following equation: Y ≥ 0.4 × X where X > 0 and X is a distance in the separating direction from an inside end of the exposed portion exposed on the upper surface of the sample separating medium, to an inside end of the sample containing medium, and Y is a distance in a direction perpendicular to the separating direction from the inside end of the exposed portion exposed on the upper surface of the sample separating medium to the connecting region; a first buffer tank containing at least part of the exposed portion; and a second buffer tank being located in such a manner that the sample separating section will be in between the second buffer tank and the exposed portion, the sample separating section having a communicating opening for communicating between the sample separating medium and the second buffer tank. a sample separating section for containing a sample separating medium for separating a sample in a separating direction, the sample separating section containing the sample separating medium in such a manner that the sample separating medium has an exposed portion at one end of a surface of the sample separating medium, the surface being in parallel with the separating direction; medium connecting means (107, 108) for connecting a sample containing medium to the sample separating medium at a connecting region on the exposed portion, the sample containing medium containing a sample, and the connecting region satisfying the following equation: Y ≥ 0.4 × X where X > 0 and X is a distance in the separating direction from an inside end of the exposed portion exposed on the upper surface of the sample separating medium, to an inside end of the sample containing medium, and Y is a distance in a direction perpendicular to the separating direction from the inside end of the exposed portion exposed on the upper surface of the sample separating medium to the connecting region; a first buffer tank containing at least part of the exposed portion; and a second buffer tank being located in such a manner that the sample separating section will be in between the second buffer tank and the exposed portion, the sample separating section having a communicating opening for communicating between the sample separating medium and the second buffer tank. where X > 0 and X is a distance in the separating direction from an inside end of the exposed portion exposed on the upper surface of the sample separating medium, to an inside end of the sample containing medium, and Y is a distance in a direction perpendicular to the separating direction from the inside end of the exposed portion exposed on the upper surface of the sample separating medium to the connecting region; a first buffer tank containing at least part of the exposed portion; and a second buffer tank being located in such a manner that the sample separating section will be in between the second buffer tank and the exposed portion, the sample separating section having a communicating opening for communicating between the sample separating medium and the second buffer tank.