Automatic transmission

An automatic transmission comprising:

• a transmission case;
• a hub which is a rotary member;
• a multi-disc brake including a first friction engagement element having first plates and a second friction engagement element having second plates, the first plates and the second plates being alternately arranged in an axial direction, the first friction engagement element being spline-fitted to an inner peripheral surface of the transmission case, the second friction engagement element being spline-fitted to the hub;
• and
• a tube, which is provided in the transmission case, that supplies lubricating oil to the first friction engagement element and the second friction engagement element, wherein
• the tube has injection holes that inject the lubricating oil toward a spline groove, which is fitted with spline teeth of the first friction engagement element on the inner peripheral surface of the transmission case, and
• the injection holes open toward a gap, which is formed between the spline groove and the spline teeth, and inject the lubricating oil to cause the lubricating oil to contact a surface of the spline groove located above the spline teeth.