Disclosed in a reading apparatus for supplying power to at least one of a plurality of superimposed RF tags and reading information from the tag while power is being supplied thereto. The apparatus includes means for generating high-frequency signals; electromagnetic wave generating means to which the high-frequency signals are input for generating electromagnetic waves from a plurality of locations, e.g., from both sides of the superimposed tags, by the high-frequency signals and causing the electromagnetic waves to interfere with each other on the tags; means for controlling the phase difference between the high-frequency signals, which are supplied to the electromagnetic wave generating means provided on both sides of the tags, in accordance with the position of a tag from which information is read; and phase shifting means for controlling the phase of at least one high-frequency signal so to produce the phase difference.