Anti-TRAIL-R1 and R2 antibodies or functional fragments thereof, having at least one property selected from the following (a) to (c) of:(a) having activity to induce apoptosis in carcinoma cells expressing TRAIL-R1 and/or TRAIL-R2;(b) not having effect on normal human cells expressing TRAIL-R1 and/or TRAIL-R2; and(c) not inducing human hepatocyte toxicity.