∵a²+b²+c²=ab+bc+ca,
∴2a²+2b²+2c²=2ab+2bc+2ca,
2a²+2b²+2c²-2ab-2bc-2ca=0
（a²-2ab+b²)+(a²-2ac+c²)+(b²-2bc+c²)=0
(a-b)²+(a-c)²+(b-c)²=0
∴(a-b)²=0,(a-c)²=0,(b-c)²=0
∴a-b=0,a-c=0,b-c=0
∴a=b=c,
即：△ABC是等边三角形.