The invention relates to a method for collecting sap from a tree. The method comprises a collection stage and an analysis stage, in which the purity of the sap being collected is determined and, on the basis of the information obtained, the collection stage is terminated. With the aid of the method, sap is produced, in which additives are not used, and which is not heat-treated, and which has, however, good preservability at room temperature. The invention also relates to an apparatus for collecting sap from a tree.