The interest in the use of fiscal policy as an effective economic policy tool has been revived recently, since the global recession of 2008 hit the world. In spite of a large empirical literature, there remains substantial uncertainty about the size and even the direction of the effects of discretionary fiscal policy. This thesis seeks to investigate the macroeconomic effects of discretionary fiscal policy in the short term, highlighting several methodologies for identifying discretionary fiscal policy. In Chapters 2 and 3, we suggest a new instrument based on the narrative approach for identifying exogenous government spending shocks: natural disaster damages and the subsequent government emergency spending. While applying our methodology to the Korean and the U.S data, we find that our instrument is not only powerful but also superior to military build-ups used by most of the literature. The relief expenditure in the wake of natural disaster has several advantages such as the similarity in scope to general government activity and the easy applicability beyond the U.S. compared to military build-ups. In the analysis of Korean fiscal policy, using our narrative method and the Structural Vector Autoregression (SVAR) model, we find that government spending shocks increase GDP, consumption, and real wage, which is in line with the New Keynesian model. We also find that the timing is crucial in identifying government spending shocks due to the anticipation effects of fiscal policy. Furthermore, while analyzing the U.S. fiscal policy both at the state as well as national level, we estimate two kinds of non-defense spending multipliers: federal (1.4~1.7) and state (1.5~2.5), which exceed the defense spending multiplier obtained in the literature using military building-ups. In Chapter 4, in regard to the study of effects of fiscal adjustment, we develop the approach based on changes in cyclically adjusted primary balance (CAPB) by including fluctuations of asset price in the CAPB measure and allowing for individual country heterogeneity in the definition of fiscal adjustment. Using our new CAPB in 20 OECD countries, we find that fiscal adjustments have contractionary effects on economic activity in the short term, which is consistent with the result based on the narrative approach. Nevertheless, our results suggest that fiscal adjustments that rely predominantly on spending cuts are less contractionary than those involving tax increases.