i believe this has already been answered other places. did you search first? anyway, it is probable that it compiled with debug information, just turn off the debug info if it is on, and that should cut the file size way down.
Because Dev-C++ uses GCC, you can add a good few options for further stripping down the executable once you've turned off the debugging information, go to:
Tools --> Compiler Options
Click on the Settings tab & go down to Linker, select Yes for strip executable
Click on Optimization (Further Optimization) Best Optimization - Yes
These make your exectuable small & good.