A bicycle force sensing device is basically provided with an attachment member, a translation detecting structure and an orientation detector. The attachment member is configured to be mounted to a bicycle bottom bracket hanger and is configured to receive and rotatably support a crank axle. The translation detecting structure is coupled to the attachment member such that the translation detecting structure senses strain on the attachment member in a first strain measurement direction and in a second strain measurement direction that is nonparallel to the first strain measurement direction. The orientation detector is coupled to the attachment member such that the orientation detector detects an orientation of the attachment member.