In this paper, we describe the joining property of welded sheets obtained by magnetic pulse welding. In this method, it is possible to weld aluminum alloy sheets to a low-carbon sheet, for example, A6061-T6 or A2017-T3. An electromagnetic force deforms the aluminum sheet, and the height of the sheet is governed by both the force and the properties of the sheet. Collision times are examined in various gap lengths for the four kinds of aluminum sheets in 2.0 kJ discharge energy experiments, and collision velocities are calculated using the collision times. The relationship between shearing load of the welded sheet and the gap length is also examined. The collision times of the four sheets are approximately equal at gap lengths less than or equal to 2.48 mm and increase in accordance with the materials property values of quasi-static process at gap lengths more than 2.48 mm. Magnetic pulse welding is phenomenon in a high strain rate and the strain rate of the sheet exceeds 10000 s^-1 as a rough estimate. It is difficult to weld the sheets with a large flow stress to the low-carbon sheet, and the welding depends on the flow stress. Therefore, the flow stress of aluminum sheet also is a factor influencing the joining property of welded sheets.