Bicycle having dual-purpose pedal

A bicycle having dual-purpose pedals, wherein a structure of a main shaft tube of said bicycle is improved, said structure comprising:

• a main shaft received in said main shaft tube, two ends of said main shaft having bearing portions, an outer diameter of one of said bearing portions diminishing and being horizontally extended to a fixing gear to form a gear portion, the outer diameter of said gear portion also diminishing and being horizontally extended to form a fixing portion;
• a first spring telescoped onto said main shaft, one end of said first spring being fixedly arranged on said main shaft, another end of said first spring having a circular hole pressed onto said main shaft;
• a gear bushing telescoped onto said fixing portion of said main shaft and correspondingly engaging said gear portion, two corresponding grooves being provided at an outside of said gear bushing;
• a crank, wherein one end thereof is pivotally connected with a pedal of said bicycle and another thereof end has a crank hole therein, a flange being provided outside said crank hole, two corresponding projective bars being arranged in said crank hole, and said projective bars being matched in said two grooves of said gear bushing;
• a second spring received in said crank hole and abutting said gear bushing;
• a washer abutting said flange of said crank hole and said second spring, a screw passing through said washer and being fixedly locked in said fixing portion of said main shaft to position said crank on said main shaft;
• and
• a fixing unit passing through said main shaft tube and fixed at a position on said main shaft tube corresponding to said circular hole of said first spring.