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 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 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 . <EOS>