A flow rate setting system of a working machine, includes: an attachment configured to be attached to the working machine; a control part configured to control a flow of hydraulic operation fluid based on a maximum flow rate of the hydraulic operation fluid being to be supplied to the attachment, the control part being mounted on the working machine; and a mobile terminal configured to communicate in wireless communication, the mobile terminal including: a first obtaining part configured to obtain identification information, the identification information being used for identifying the attachment; a second obtaining part configured to obtain the maximum flow rate of the attachment; and an output part configured to output the identification information and the maximum flow rate to the working machine in the wireless communication, the identification information being obtained by the first obtaining part, the maximum flow rate being obtained by the second obtaining part.