A bicycle crank arm is provided that is a light, highly strong, highly rigid and highly designed in a complex shape. The bicycle crank arm has a crank axle mounting end portion, a central crank body portion and a pedal mounting end portion. The hollow bicycle crank arm is preferably a one-piece, unitary member that is produced by a tube hydroforming method. The hollow bicycle crank arm has a crank axle attachment part located within the crank axle mounting end portion and a pedal spindle attachment part located within the pedal mounting end portion. The mounting end portions have a crank axle hole and a pedal spindle hole, respectively, with outside diameters that are smaller than the attachment parts, respectively.