To provide a method for determining nutrient tube's accession to a stomach, by which a determination can speedily, securely and safely be made whether a nutrient tube has reached a stomach before a nutrient is supplied to the stomach through the nutrient tube.

The method includes: a step in which before a nutrient is supplied to a stomach through an enteral nutrient tube 3, this tube 3 is disposed in the opening 7 of a leading end, which is the exit side for the nutrient, while a detecting portion of a pH electrode 8 is exposed in advance, and then the tube 3 is advanced into a body by a predetermined distance and dwelled there; a step in which the pH electrode 8 measures the pH of an object to be in contact with the detecting part; and a step in which it is determined whether the opening 7 of the leading end of the tube 3 has reached the stomach from the value of the pH obtained by the measurement.