The instant disclosure relates to a light bulb, which includes a connecting cap, a heat-dissipating seat, a LED module, a light-guiding member, and a bulb. The heat-dissipating seat is disposed on one end of the connecting cap, and the LED module is disposed on the heat-dissipating seat. The light-guiding member is connected to the heat-dissipating seat and covers the LED module. At least one microstructure is formed on the surface of the light-guiding member for changing the light projection path. The bulb is arranged over the light-guiding member. Thereby, the light bulb can illuminate a wider area and achieve more uniform brightness. A light-guiding member is also disclosed.