A working machine comprising: a machine body, and a working equipment mounted on the machine body; the machine body comprising: a lower traveling body, and an upper slewing body provided on the lower traveling body so as to be able to slew; the working equipment being mounted on the upper slewing body; the upper slewing body comprising: a slewing frame having a bottom plate; an engine; an exhaust gas cleaning apparatus that executes reduction treatment on a predetermined oxide in an exhaust gas of the engine by injecting a liquid reducing agent; a first tank that stores a liquid reducing agent; a reducing agent pump that feeds the liquid reducing agent stored in the first tank to the exhaust gas cleaning apparatus; a cooling fan; an opening section disposed on the bottom plate of the slewing frame; and a duct section that leads outside air taken from the opening section to the cooling fan; the cooling fan being operable to draw in the outside air from the opening section into the duct section to cool the reducing agent pump; wherein the bottom plate is formed with an access opening section that enables access to the reducing agent pump therethrough, and either (a) the access opening section is the opening section, or (b) a removable opening/closing member is provided for opening and closing the access opening section, and the opening/closing member is formed with the opening section. a machine body, and a working equipment mounted on the machine body; the machine body comprising: a lower traveling body, and an upper slewing body provided on the lower traveling body so as to be able to slew; a lower traveling body, and an upper slewing body provided on the lower traveling body so as to be able to slew; the working equipment being mounted on the upper slewing body; the upper slewing body comprising: a slewing frame having a bottom plate; an engine; an exhaust gas cleaning apparatus that executes reduction treatment on a predetermined oxide in an exhaust gas of the engine by injecting a liquid reducing agent; a first tank that stores a liquid reducing agent; a reducing agent pump that feeds the liquid reducing agent stored in the first tank to the exhaust gas cleaning apparatus; a cooling fan; an opening section disposed on the bottom plate of the slewing frame; and a duct section that leads outside air taken from the opening section to the cooling fan; a slewing frame having a bottom plate; an engine; an exhaust gas cleaning apparatus that executes reduction treatment on a predetermined oxide in an exhaust gas of the engine by injecting a liquid reducing agent; a first tank that stores a liquid reducing agent; a reducing agent pump that feeds the liquid reducing agent stored in the first tank to the exhaust gas cleaning apparatus; a cooling fan; an opening section disposed on the bottom plate of the slewing frame; and a duct section that leads outside air taken from the opening section to the cooling fan; the cooling fan being operable to draw in the outside air from the opening section into the duct section to cool the reducing agent pump; wherein the bottom plate is formed with an access opening section that enables access to the reducing agent pump therethrough, and either (a) the access opening section is the opening section, or (b) a removable opening/closing member is provided for opening and closing the access opening section, and the opening/closing member is formed with the opening section. (a) the access opening section is the opening section, or (b) a removable opening/closing member is provided for opening and closing the access opening section, and the opening/closing member is formed with the opening section.