A grain classifying device for accurately classifying the grains of uniform length, and an adhesive containing grains classified by the device and capable of connecting electrodes under a low pressure and being applicable to electrodes arranged in fine pitches. The grain classifying device (1) includes a dispersing means (2) for dispersing a plurality of grains (P). A grain orienting means (3) orients each of the dispersed grains in a transfer direction (X) of the grains (P) while spacing the grains apart from one another in the transfer direction (X) of the grains. A grain length measuring means (4) measures the length of each of the grains (P) oriented in the transfer direction (X). A grain separation means (5) separates the grains (P) having a predetermined length based on data related to the lengths of the measured grains (P).