In recent years, durable highway bridge composite decks such as steel and concrete or FRP and concrete composites have been encouraged to construct in Japan. In this study, the steel and concrete composite deck arranged channel shape steel members in the transverse direction on the top surface of the bottom steel plate has been investigated by the authors. By the arrangement of channel shape steel members welded to the bottom steel plate, the steel and concrete composite deck with hollows in the concrete becomes to be more lightweight than typical types of steel and concrete composite decks. For highway bridge decks, it is significantly important to verify the fatigue strength of welded joints. In this paper, fatigue tests on the welded joint between the channel shape steel and the steel plate were carried out under the tensile fatigue stress. Both stress concentration factors at the weld root and toe of the filet welded joint conducted herein were approximately same values. A fatigue crack was initiated from the weld root and propagated into the steel plate due to the existing of a small void at the weld root. Finally, stress range versus fatigue life diagram (S-N curve) was obtained and the fatigue strength was compared with the Fatigue Design Recommendations given by Japanese Society of Steel Construction. As a result, the fatigue strength of the welded joint studied in this study was appropriate to the C grade of the Fatigue Design Recommendations.