A monitoring device and a monitoring method for an injection molding machine, in which a trend chart is displayed on a common axis so that changes of set values of molding conditions and changes of measured values of monitoring items can be grasped correspondingly. A history of the measured values of the monitoring items is stored, and a change history of the set values of the molding conditions is also stored. An operator sets monitoring items and molding condition items to be displayed. In doing this, the operator sets a display range such that molding condition items having changed set values within the display range are displayed and selected. Alternatively, coefficients of correlation between the measured values of the selected monitoring items and the set values of the molding conditions are obtained, and the molding condition items are displayed in the order of priority of correlation and selected. For example, a metering time, minimum cushion amount, and peak pressure are selected as the monitoring items, and a first stage injection speed and barrel 3 temperature as the molding condition items. Thus, the trend chart is displayed with a time base on its abscissa axis, and the influence of the set values on the measured values can be grasped with ease.