A hydraulic circuit for heavy equipment is disclosed, which utilizes a hydraulic fluid supplied from a hydraulic pump for driving a cooling fan, as a pilot signal pressure, without installing a separate constant displacement pilot pump for supplying the pilot signal pressure to a control valve for controlling the hydraulic fluid to be supplied to a working device such as a boom. The hydraulic circuit includes first to third hydraulic pumps connected to an engine; a first control valve installed in a flow path of the first hydraulic pump; a second control valve installed in a flow path of the second hydraulic pump; a hydraulic motor connected to the third hydraulic pump; a cooling fan, connected to the hydraulic motor, for discharging cooling wind to an oil cooler; a temperature sensor for detecting a temperature of the hydraulic fluid in the hydraulic tank; an electric relief valve, installed in a drain flow path of the third hydraulic pump, for variably controlling a rotation velocity of the cooling fan; a controller for controlling the hydraulic pressure that drives the hydraulic motor; and a pilot pressure generator, installed in a pilot flow path branched and connected to a flow path of the third hydraulic pump, for supplying a pilot signal pressure to the first and second control valves when shifting.