A variable valve timing controller has a phase adjusting mechanism. The phase adjusting mechanism includes a first rotating member and second rotating member which are respectively rotate in synchronization with a driving shaft and a driven shaft of an engine, a first arm rotatably connected with the first rotating member, and a second arm rotatably connected with the second rotating member and the first arm. In the first arm, a distance between connecting points is defined as a distance L1. In the second arm, a distance between connecting points is defined as a distance L2. A ratio L1/L2 is defined within a range of 0.5 to 2.