The invention relates to a seal examining method of a packer and a seal examining device used in the method. The seal examining device comprises a hollow pipe body, wherein the hollow pipe body is internally provided with inner holes which are used for being communicated with pipe cavities of corresponding oil pipes; the periphery of the hollow pipe body is provided with a storage cavity for storing a seal examining reagent; the cavity wall of the storage cavity is provided with a reagent outflow channel through which the seal examining reagent flows into a plugging space formed by the packer to be examined; and the seal examining device also comprises a switch mechanism for controlling the connection and disconnection of the reagent outflow channel. The invention can judge the plugging effect of the packer to be examined accurately.