Double-speed image signal display method and display unit, and TV set

A flickerless television receiver displays image signals having the horizontal/vertical scanning frequencies thereof increased to two times the horizontal/vertical scanning frequencies of the broadcast signals to be received. Flickerless display performance can be confirmed with a single television receiver by generating signals to extract every other field for image displaying and showing two kinds of image signals, namely double-speed image signal and extracted image signal. A display unit displays double-speed image signals having horizontal and vertical scanning frequencies of image signals increased to two tunes by conversion, wherein extracted image signals formed by extracting every other field or frame from screen images are generated and two kinds of images formed of the double-speed image signals and extracted image signals are simultaneously displayed on one screen.