In the typical Blumlein-type nitrogen laser, the dependence of laser pulse width on pressure, a repetition rate and electrode separation is discussed. As the pressure increases, the pulse width decreases owing to the increase of the discharge channel resistance. The repetition rate of the laser pulse is adjusted by using a thyratron as a trigger switch. The pulse width increases with the increasing repetition rate. When the repetition rate exceeds a certain threshold, the laser emission stops. This reason is discussed with respect to a destruction time of metastables of nitrogen molecules. The effects caused by changing electrode separation and adding the third electrode are also discussed. The third electrode makes the pulse width short by pre-ionization.