A control apparatus for a diesel engine provided with at least a glow plug and a turbocharger, including: a supercharging pressure detecting means for detecting a supercharging pressure; a water temperature sensor for detecting a water temperature; an intake air temperature sensor for detecting an intake air temperature (Tl); and a controller comprising: a target supercharging pressure setting section for setting a target supercharging pressure; and a supercharging pressure control section configured to control the turbocharger in order that the supercharging pressure becomes the target supercharging pressure, characterized in that the control apparatus further includes a surface temperature detecting means for detecting a surface temperature of the glow plug and in that the controller further comprises: a target surface temperature setting section for setting a target surface temperature of the glow plug; a duty control section of the glow plug such that the detected surface temperature of the glow plug is becoming the target surface temperature of the glow plug; and a neighboring temperature estimating section configured to estimate a temperature of a neighborhood of a glow plug that heats an interior of a cylinder upon startup based at least on the target surface temperature of the glow plug, the detected water temperature, and the detected intake air temperature, wherein the target supercharging pressure is determined from a map based on the estimated temperature of the neighborhood of the glow plug and the supercharging pressure. a supercharging pressure detecting means for detecting a supercharging pressure; a water temperature sensor for detecting a water temperature; an intake air temperature sensor for detecting an intake air temperature (Tl); and a controller comprising: a target supercharging pressure setting section for setting a target supercharging pressure; and a supercharging pressure control section configured to control the turbocharger in order that the supercharging pressure becomes the target supercharging pressure, a target supercharging pressure setting section for setting a target supercharging pressure; and a supercharging pressure control section configured to control the turbocharger in order that the supercharging pressure becomes the target supercharging pressure, characterized in that the control apparatus further includes a surface temperature detecting means for detecting a surface temperature of the glow plug and in that the controller further comprises: a target surface temperature setting section for setting a target surface temperature of the glow plug; a duty control section of the glow plug such that the detected surface temperature of the glow plug is becoming the target surface temperature of the glow plug; and a neighboring temperature estimating section configured to estimate a temperature of a neighborhood of a glow plug that heats an interior of a cylinder upon startup based at least on the target surface temperature of the glow plug, the detected water temperature, and the detected intake air temperature, a target surface temperature setting section for setting a target surface temperature of the glow plug; a duty control section of the glow plug such that the detected surface temperature of the glow plug is becoming the target surface temperature of the glow plug; and a neighboring temperature estimating section configured to estimate a temperature of a neighborhood of a glow plug that heats an interior of a cylinder upon startup based at least on the target surface temperature of the glow plug, the detected water temperature, and the detected intake air temperature, wherein the target supercharging pressure is determined from a map based on the estimated temperature of the neighborhood of the glow plug and the supercharging pressure.