To obtain through a simple process an alkaline earth metal aluminate-or alkaline earth metal silicate-based luminous phosphor with narrow particle size distribution, causing no decline in afterglow luminance even if subjected to mixing/pulverization, and having particle shape suitable as a pigment.

This luminous phosphor is such one as to have a matrix crystal structure of akermanite type composed of R' (at least one element selected from the group consisting of Ca, Sr and Ba), Mg, Si, O and N and also contain Eu as activator and Dy or the like as coactivator. This luminous phosphor is obtained by producing a matrix crystal of akermanite-type structure through burning a strontium nitrate-contg. stock, or by spraying a stock in the form of a solution or suspension containing the respective constitutive elements into droplets which are then heated in an oxidative, inert or reductive atmospheric airflow. This luminous phosphor has a new Mohs scale of <1, having such an afterglow characteristic as to be ≥200 mCd/m2 in luminance 2 min after termination of 30 min irradiation at 1,000 lux using a daylight fluorescent lamp.